Articles de revues : « Magnetic Behaviour - Ultra-thin Epitaxial Films »

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YANG, T. R., G. ILONCA, V. TOMA, P. BALINT et M. BODEA. « MAGNETIC RESISTIVITY IN Bi2Sr2Ca(Cu1-xCox)2Od EPITAXIAL THIN FILMS ». International Journal of Modern Physics B 21, n^o 01 (10 janvier 2007) : 127–32. http://dx.doi.org/10.1142/s0217979207035923.

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The scaling behavior of the effective activation energy of high-quality epitaxial c-oriented Bi 2 Sr 2 Ca ( Cu 1-x Co x)2 O d thin films with 0≤x ≤0.025 has been studied as a function of temperature and magnetic field. For all samples, the effective activation energy scales as U(T, μoH)=Uo(1-T/T c )mHn with exponent m=1.25±0.03, n=-1/2 and the field scaling 1/μoH and -UμoH for thick films and ultra thin films, respectively. The results are discussed taking into account of the influence of the Co substitution with a model in which U(T, H) arises from plastic deformations of the viscous flux liquid above the vortex-glass transition temperature.

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Fähnle, Manfred, et Matej Komelj. « Second-order magnetoelastic effects : From the Dirac equation to the magnetic properties of ultrathin epitaxial films for magnetic thin-film applications ». International Journal of Materials Research 93, n^o 10 (1 octobre 2002) : 970–73. http://dx.doi.org/10.1515/ijmr-2002-0168.

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Abstract It has always been the endeavour of Professor Kronmüller to combine various methods in order to attain a comprehensive understanding of a physical phenomenon on all relevant scales. In this spirit, we combine the phenomenological nonlinear theory of magnetoelasticity with the relativistic density functional electron theory to describe the magnetoelastic behaviour of epitaxial films. We explain the two already performed cantilever bending beam experiments on the magnetoelasticity and underpin the assumption that second-order magnetoelastic effects are very important for epitaxial Fe films. A complete set of six cantilever experiments is introduced which allows to calculate the intrinsic first- and second-order magnetoelastic constants for cubic materials, and these constants are calculated ab initio for Fe, face-centred cubic Co, Ni, Ni3Fe and CsCl-type CoFe.

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Sando, D., A. Agbelele, C. Daumont, D. Rahmedov, W. Ren, I. C. Infante, S. Lisenkov et al. « Control of ferroelectricity and magnetism in multi-ferroic BiFeO 3 by epitaxial strain ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 372, n^o 2009 (28 février 2014) : 20120438. http://dx.doi.org/10.1098/rsta.2012.0438.

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Recently, strain engineering has been shown to be a powerful and flexible means of tailoring the properties of ABO 3 perovskite thin films. The effect of epitaxial strain on the structure of the perovskite unit cell can induce a host of interesting effects, these arising from either polar cation shifts or rotation of the oxygen octahedra, or both. In the multi-ferroic perovskite bismuth ferrite (BiFeO 3 –BFO), both degrees of freedom exist, and thus a complex behaviour may be expected as one plays with epitaxial strain. In this paper, we review our results on the role of strain on the ferroic transition temperatures and ferroic order parameters. We find that, while the Néel temperature is almost unchanged by strain, the ferroelectric Curie temperature strongly decreases as strain increases in both the tensile and compressive ranges. Also unexpected is the very weak influence of strain on the ferroelectric polarization value. Using effective Hamiltonian calculations, we show that these peculiar behaviours arise from the competition between antiferrodistortive and polar instabilities. Finally, we present results on the magnetic order: while the cycloidal spin modulation present in the bulk survives in weakly strained films, it is destroyed at large strain and replaced by pseudo-collinear antiferromagnetic ordering. We discuss the origin of this effect and give perspectives for devices based on strain-engineered BiFeO 3 .

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Kurdi, Samer, Yuya Sakuraba, Keisuke Masuda, Hiroo Tajiri, Bhaskaran Nair, Guillaume F. Nataf, Mary E. Vickers et al. « Quantitative atomic order characterization of a Mn₂FeAl Heusler epitaxial thin film ». Journal of Physics D : Applied Physics 55, n^o 18 (10 février 2022) : 185305. http://dx.doi.org/10.1088/1361-6463/ac4e32.

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Abstract In this work, we investigate the effect of anti-site disorder on the half-metallic properties of a Mn2FeAl Heusler alloy thin film. The film was grown on TiN-buffered MgO 001 substrates via magnetron sputtering. A detailed structural characterization using x-ray diffraction (XRD) and anomalous XRD showed that the film crystallizes in the partially disordered L21 B structure with 33% disorder between the Mn(B) and Al(D) sites. We measure a positive anisotropic magnetoresistance in the film, which is an indication of non-half metallic behaviour. Our x-ray magnetic circular dichroism sum rules analysis shows that Mn carries the magnetic moment in the film, with a positive Fe moment. Experimentally determined moments correspond most closely with those found by density functional calculated for the L21 B structure with Mn(B) and Al(D) site disorder, matching the experimental structural analysis. We thus attribute the deviation from half-metallic behaviour to the formation of the L21 B structure. To realize a half-metallic Mn2FeAl film it is important that the inverse Heusler XA structure is stabilized with minimal anti-site atomic disorder.

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Li, Yongkuan, Xinxing Liu, Dan Wen, Kai Lv, Gang Zhou, Yue Zhao, Congkang Xu et Jiangyong Wang. « Growth of c-plane and m-plane aluminium-doped zinc oxide thin films : epitaxy on flexible substrates with cubic-structure seeds ». Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 76, n^o 2 (19 mars 2020) : 233–40. http://dx.doi.org/10.1107/s2052520620002668.

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Manufacturing high-quality zinc oxide (ZnO) devices demands control of the orientation of ZnO materials due to the spontaneous and piezoelectric polarity perpendicular to the c-plane. However, flexible electronic and optoelectronic devices are mostly built on polymers or glass substrates which lack suitable epitaxy seeds for the orientation control. Applying cubic-structure seeds, it was possible to fabricate polar c-plane and nonpolar m-plane aluminium-doped zinc oxide (AZO) films epitaxially on flexible Hastelloy substrates through minimizing the lattice mismatch. The growth is predicted of c-plane and m-plane AZO on cubic buffers with lattice parameters of 3.94–4.63 Å and 5.20–5.60 Å, respectively. The ∼80 nm-thick m-plane AZO film has a resistivity of ∼11.43 ± 0.01 × 10−4 Ω cm, while the c-plane AZO film shows a resistivity of ∼2.68 ± 0.02 × 10−4 Ω cm comparable to commercial indium tin oxide films. An abnormally higher carrier concentration in the c-plane than in the m-plane AZO film results from the electrical polarity along the c-axis. The resistivity of the c-plane AZO film drops to the order of 10−5 Ω cm at 500 K owing to the semiconducting behaviour. Epitaxial AZO films with low resistivities and controllable orientations on flexible substrates offer optimal transparent electrodes and epitaxy seeds for high-performance flexible ZnO devices.

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Venzke, S., R. B. van Dover, Julia M. Phillips, E. M. Gyorgy, T. Siegrist, C.-H. Chen, D. Werder et al. « Epitaxial growth and magnetic behavior of NiFe2O4 thin films ». Journal of Materials Research 11, n^o 5 (mai 1996) : 1187–98. http://dx.doi.org/10.1557/jmr.1996.0153.

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Thin films of NiFe2O4 were deposited on SrTiO3 (001) and Y0.15Zr0.85O2 (yttria-stabilized zirconia) (001) and (011) substrates by 90°-off-axis sputtering. Ion channeling, x-ray diffraction, and transmission electron microscopy studies reveal that films grown at 600 °C consist of ∼300 Å diameter grains separated by thin regions of highly defective or amorphous material. The development of this microstructure is attributed to the presence of rotated or displaced crystallographic domains and is comparable to that observed in other materials grown on mismatched substrates (e.g., GaAs/Si or Ba2YCu3O7/MgO). Postdeposition annealing at 1000 °C yields films that are essentially single crystal. The magnetic properties of the films are strongly affected by the structural changes; unannealed films are not magnetically saturated even in an applied field of 55 kOe, while the annealed films have properties comparable to those of bulk, single crystal NiFe2O4. Homoepitaxial films grown at 400 °C also are essentially single crystal.

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Wang, Weiyuan, Jiyu Fan, Huan Zheng, Jing Wang, Hao Liu, Caixia Wang, Chunlan Ma, Langsheng Ling, Jingtao Xu et Hao Yang. « Two conductive mechanisms in LaMnO3 thin film : Adiabatic and nonadiabatic small polaronic hopping ». Modern Physics Letters B 35, n^o 19 (24 juin 2021) : 2150310. http://dx.doi.org/10.1142/s0217984921503103.

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We have presented the structural, surface morphology, magnetic and resistivity data for perovskite LaMnO3 epitaxial thin films which are fabricated on well-oriented (001) LaAlO3 substrates by pulsed laser deposition technique. X-ray diffraction [Formula: see text]–[Formula: see text] linear scans and reciprocal space mapping measurement confirm that the out-of-plane and in-plane epitaxial relationship are LMO(001)/LAO(001) and LMO(110)/LAO(110), respectively. Surface roughness determined by atomic force microscopy was no more than 0.3 nm. In the whole studied temperature range, all films only show a paramagnetic behavior instead of any magnetic phase transitions. Correspondingly, the electron transport behaviors always exhibit an insulting state as the temperature changes from high to low. However, we find that none of theoretical models can individually be used to understand their conductive mechanisms. Further studies indicated that charge carries of high and low temperature region obey adiabatic and nonadiabatic small polaronic hopping mechanisms, respectively. This finding offers new ways of exploiting the abnormal ferromagnetism in LaMnO3 multilayer thin films.

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ILONCA, G., A. V. POP, T. JURCUT, E. MOCOCEAN, C. BEIUSEANU, C. LUNG, G. STIUFIUC, R. STIUFIUC, M. YE et R. DELTOUR. « MAGNETIC FIELD AND TEMPERATURE DEPENDENCE OF THERMALLY ACTIVATED DISSIPATION IN EPITAXIAL THIN FILMS OF YBa2 (Cu1-xZnx)3O7-d ». Modern Physics Letters B 15, n^o 22 (20 septembre 2001) : 949–57. http://dx.doi.org/10.1142/s0217984901002786.

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The scaling behavior of the effective activation energy of high-quality epitaxial c-oriented YBa 2( Cu 1-x Zn x)3 O 7-d thin films has been studied as a function of temperature and magnetic field. For all samples, the effective activation energy scales as U(T, μ0H) = U0(1 - T/T c )mHn with exponent m = 1.6 ± 0.02 - 1.3 ± 0.02 and the field scaling 1/μ0H and - ln μ0H for thick films and ultrathin films, respectively. The results are discussed taking account of the influence of the Zn substitution on the flux pinning in epitaxial YBa 2( Cu 1-x Zn x)3 O 7-d thin films.

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Sarkar, Tanushree, Suja Elizabeth et P. S. Anil Kumar. « Growth of ordered and disordered epitaxial thin films of Lu2MnNiO6 using (0 0 1)-LaAlO3 and (0 0 1)-SrTiO3 substrates : Observation of six monoclinic in-plane twin variants and glassy magnetic behaviour ». Journal of Magnetism and Magnetic Materials 521 (mars 2021) : 167514. http://dx.doi.org/10.1016/j.jmmm.2020.167514.

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Boukelkoul, M., M. Kharoubi et A. Haroun. « Magnetic and magneto-optical properties of ultrathin films of iron epitaxied on iridium (001) ». Canadian Journal of Physics 86, n^o 12 (1 décembre 2008) : 1421–26. http://dx.doi.org/10.1139/p08-103.

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We have theoretically studied the structural, magnetic, and magneto-optical behaviours of Fe ultra-thin films pseudomorphically epitaxied on semi-infinite Ir(001). The magnetic film crystallizes in the body-centered tetragonal (bct) structure with a tetragonality ratio 1.21. The new crystalline structure of iron in the magnetic film enhances the magnetic properties and a correlation between the interlayer spacing and the magnetic moment is found. The calculation of the magnetic properties shows a ferromagnetic interlayer coupling. The polar magneto-optical Kerr effect (P-MOKE) spectra are calculated over a photon energy range extended to 10~eV. The microscopic origin of the most interesting features is explained from interband transitions in various regions of the Brillouin zone.PACS Nos.: 78.20.Bh, 78.20.Ls

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Zheng, Xin Yu, Lauren J. Riddiford, Jacob J. Wisser, Satoru Emori et Yuri Suzuki. « Ultra-low magnetic damping in epitaxial Li0.5Fe2.5O4 thin films ». Applied Physics Letters 117, n^o 9 (31 août 2020) : 092407. http://dx.doi.org/10.1063/5.0023077.

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Wang, Hailin, Carlos Frontera, Benjamín Martínez et Narcís Mestres. « Rapid Thermal Annealing of Double Perovskite Thin Films Formed by Polymer Assisted Deposition ». Materials 13, n^o 21 (4 novembre 2020) : 4966. http://dx.doi.org/10.3390/ma13214966.

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The annealing process is an important step common to epitaxial films prepared by chemical solution deposition methods. It is so because the final microstructure of the films can be severely affected by the precise features of the thermal processing. In this work we analyze the structural and magnetic properties of double perovskite La2CoMnO6 and La2NiMnO6 epitaxial thin films prepared by polymer-assisted deposition (PAD) and crystallized by rapid thermal annealing (RTA). It is found that samples prepared by RTA have similar values of saturation magnetization and Curie temperature to their counterparts prepared by using conventional thermal annealing (CTA) processes, thus indicating low influence of the heating rates on the B-B’ site cationic ordering of the A2BB’O6 double perovskite structure. However, a deeper analysis of the magnetic behavior suggested some differences in the actual microstructure of the films.

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Hajihoseini, Hamidreza, Movaffaq Kateb, Snorri Þorgeir Ingvarsson et Jon Tomas Gudmundsson. « Oblique angle deposition of nickel thin films by high-power impulse magnetron sputtering ». Beilstein Journal of Nanotechnology 10 (20 septembre 2019) : 1914–21. http://dx.doi.org/10.3762/bjnano.10.186.

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Background: Oblique angle deposition is known for yielding the growth of columnar grains that are tilted in the direction of the deposition flux. Using this technique combined with high-power impulse magnetron sputtering (HiPIMS) can induce unique properties in ferromagnetic thin films. Earlier we have explored the properties of polycrystalline and epitaxially deposited permalloy thin films deposited under 35° tilt using HiPIMS and compared it with films deposited by dc magnetron sputtering (dcMS). The films prepared by HiPIMS present lower anisotropy and coercivity fields than films deposited with dcMS. For the epitaxial films dcMS deposition gives biaxial anisotropy while HiPIMS deposition gives a well-defined uniaxial anisotropy. Results: We report on the deposition of 50 nm polycrystalline nickel thin films by dcMS and HiPIMS while the tilt angle with respect to the substrate normal is varied from 0° to 70°. The HiPIMS-deposited films are always denser, with a smoother surface and are magnetically softer than the dcMS-deposited films under the same deposition conditions. The obliquely deposited HiPIMS films are significantly more uniform in terms of thickness. Cross-sectional SEM images reveal that the dcMS-deposited film under 70° tilt angle consists of well-defined inclined nanocolumnar grains while grains of HiPIMS-deposited films are smaller and less tilted. Both deposition methods result in in-plane isotropic magnetic behavior at small tilt angles while larger tilt angles result in uniaxial magnetic anisotropy. The transition tilt angle varies with deposition method and is measured around 35° for dcMS and 60° for HiPIMS. Conclusion: Due to the high discharge current and high ionized flux fraction, the HiPIMS process can suppress the inclined columnar growth induced by oblique angle deposition. Thus, the ferromagnetic thin films obliquely deposited by HiPIMS deposition exhibit different magnetic properties than dcMS-deposited films. The results demonstrate the potential of the HiPIMS process to tailor the material properties for some important technological applications in addition to the ability to fill high aspect ratio trenches and coating on cutting tools with complex geometries.

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Sharma, Yogesh, Elizabeth Skoropata, Binod Paudel, Kyeong Tae Kang, Dmitry Yarotski, T. Zac Ward et Aiping Chen. « Epitaxial Stabilization of Single-Crystal Multiferroic YCrO3 Thin Films ». Nanomaterials 10, n^o 10 (21 octobre 2020) : 2085. http://dx.doi.org/10.3390/nano10102085.

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We report on the growth of stoichiometric, single-crystal YCrO3 epitaxial thin films on (001) SrTiO3 substrates using pulsed laser deposition. X-ray diffraction and atomic force microscopy reveal that the films grew in a layer-by-layer fashion with excellent crystallinity and atomically smooth surfaces. Magnetization measurements demonstrate that the material is ferromagnetic below 144 K. The temperature dependence of dielectric permittivity shows a characteristic relaxor-ferroelectric behavior at TC = 375–408 K. A dielectric anomaly at the magnetic transition temperature indicates a close correlation between magnetic and electric order parameters in these multiferroic YCrO3 films. These findings provide guidance to synthesize rare-earth, chromite-based multifunctional heterostructures and build a foundation for future studies on the understanding of magnetoelectric effects in similar material systems.

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Kalinowski, R., C. Meyer, A. Wawro et L. T. Baczewski. « Magnetic anisotropy in MBE-grown epitaxial gadolinium ultra-thin films ». Thin Solid Films 367, n^o 1-2 (mai 2000) : 189–92. http://dx.doi.org/10.1016/s0040-6090(00)00670-2.

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SENZ, V., A. KLEIBERT et J. BANSMANN. « TRANSVERSE MAGNETO-OPTICAL KERR EFFECT IN THE SOFT X-RAY REGIME OF ULTRATHIN IRON FILMS AND ISLANDS ON W(110) ». Surface Review and Letters 09, n^o 02 (avril 2002) : 913–19. http://dx.doi.org/10.1142/s0218625x02003159.

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The transverse magneto-optical Kerr effect (T-MOKE) in the soft X-ray regime is used to investigate the magnetic properties of ultrathin epitaxial Fe(110) films and thermally created epitaxial Fe islands on W(110). The measurements have been carried out at the Fe 2p core levels with tunable, linearly polarized synchrotron radiation. Besides the chemical selectivity T-MOKE at core levels is characterized by a much larger sensitivity compared to the visible regime. We have analyzed the transition from thin films to a three-dimensional island system at a thickness of 4 ML and the magnetic behavior when increasing the iron coverage to 8 ML. The Fe island system is characterized by a rotation of the easy magnetization axis in this coverage regime.

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Sanbou, Katsutoshi, Keita Sakuma, Tetsuya Miyawaki, Kenji Ueda et Hidefumi Asano. « Epitaxial thin films of ordered double perovskite SrLaVMoO6 ». MRS Proceedings 1454 (2012) : 21–26. http://dx.doi.org/10.1557/opl.2012.1237.

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ABSTRACTEpitaxial thin films of SrLaVMoO6 with an ordered double perovskite structure have been grown on (001) and (111) SrTiO3 substrates by magnetron sputtering. The optimized (111) film exhibited a clear (111) diffraction peak, which is a superlattice reflection of double perovskite unite cell, indicating clear B-site ordering. Temperature dependences of resistivity ρ show metallic behavior and transition point at 140~150 K, of which behavior is reminiscent of the electrical properties of materials showing long-range magnetic or antiferromagnetic order. XPS results of the Mo 3d core level spectra are discussed in terms of the B-site ordering and oxygen nonstoichiometry.

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Meyers, D., E. J. Moon, M. Kareev, I. C. Tung, B. A. Gray, Jian Liu, M. J. Bedzyk, J. W. Freeland et J. Chakhalian. « Epitaxial stabilization of ultra-thin films of EuNiO3 ». Journal of Physics D : Applied Physics 46, n^o 38 (4 septembre 2013) : 385303. http://dx.doi.org/10.1088/0022-3727/46/38/385303.

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Kim, You Jin, Shinya Konishi, Yuichiro Hayasaka, Ryo Ota, Ryosuke Tomozawa et Katsuhisa Tanaka. « Magnetic properties of epitaxial TmFe2O4 thin films with an anomalous interfacial structure ». Journal of Materials Chemistry C 8, n^o 34 (2020) : 11704–14. http://dx.doi.org/10.1039/d0tc01367f.

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Epitaxial TmFe₂O₄ thin film with self-assembled interface structure was grown on yttria-stabilized zirconia substrate. TmFe₂O₄ phase itself shows glassy behavior and the interface leads to the exchange bias effect.

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Zhang, Jing, Peng Shi, Mingmin Zhu, Ming Liu, Wei Ren et Zuoguang Ye. « Structural and magnetic properties of La0.7Sr0.3MnO3 ferromagnetic thin film grown on PMN-PT by sol–gel method ». Journal of Advanced Dielectrics 07, n^o 04 (août 2017) : 1750029. http://dx.doi.org/10.1142/s2010135x17500291.

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We report the preparation of epitaxial La[Formula: see text]Sr[Formula: see text]MnO3 thin films grown on (001)-oriented 0.72Pb(Mg[Formula: see text]Nb[Formula: see text]O3-0.28PbTiO3 substrates by the sol–gel technique. The phase structure, magnetic properties and magnetoresistance of the samples are investigated by using high solution X-ray diffraction, atomic force microscopy, physical property measurement system, respectively. The La[Formula: see text]Sr[Formula: see text]MnO3 thin films display a well-defined hysteresis loop and typical ferromagnetism behavior at lower temperature. High magnetoresistance at 5[Formula: see text]T of 42% appears at 227[Formula: see text]K for La[Formula: see text]Sr[Formula: see text]MnO3 thin film.

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Harshavardhan, K. S., M. Rajeswari, D. M. Hwang, C. Y. Chen, T. Sands et T. Venkatesan. « Comparison of the critical current anisotropy in epitaxial YBa2Cu3O7−x films on (100) LaAlO3 and (100) yttria stabilized zirconia ». Journal of Materials Research 9, n^o 2 (février 1994) : 270–74. http://dx.doi.org/10.1557/jmr.1994.0270.

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The angular magnetic field dependence of the critical current density JC(θ) of epitaxial YBa2Cu3O7 thin films is presented in the temperature regime close to Tc. The high temperature behavior of Jc(θ) shows features that are significantly different from the earlier observations at lower temperatures. A comparison between the films on (100) LaAlO3 and (100) yttria stabilized zirconia (YSZ) indicates significant differences that may be attributed to the differences in the microstructure of the films on the two substrates. In particular, the observation of enhanced pinning in the films on YSZ may be due to the pinning effects of the low angle grain boundaries present in these films.

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Kan, Daisuke, Takahiro Moriyama, Ryotaro Aso, Shinji Horai et Yuichi Shimakawa. « Triaxial magnetic anisotropy and Morin transition in α-Fe₂O₃ epitaxial films characterized by spin Hall magnetoresistance ». Applied Physics Letters 120, n^o 11 (14 mars 2022) : 112403. http://dx.doi.org/10.1063/5.0087643.

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We grew epitaxial thin films of hematite (α-Fe2O3) on (0 0 0 1) Al2O3 substrates by pulsed laser deposition and investigated their magnetic properties. α-Fe2O3 films grown at lower temperatures are found to undergo the Morin transition at higher temperatures, implying that lowering the growth temperature and managing lattice defects associated with strain relaxation are key to realizing Morin transition. We also characterized films' magnetic properties by spin Hall magnetoresistance (SMR). We show that tri-axial magnetic anisotropy can be detected as SMR features having a 60° period with respect to in-plane magnetic field rotations. Furthermore, a large change in SMR ratio associated with Néel vector re-orientation due to Morin transition is seen. Details of SMR properties for α-Fe2O3 films and their analysis results, including the influence of the fabrication process on SMR behaviors, are discussed.

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Lucas, Irene, Noelia Marcano, Thomas Prokscha, César Magén, Rubén Corcuera, Luis Morellón, José M. De Teresa, M. Ricardo Ibarra et Pedro A. Algarabel. « Spin Glass State in Strained La2/3Ca1/3MnO3 Thin Films ». Nanomaterials 12, n^o 20 (18 octobre 2022) : 3646. http://dx.doi.org/10.3390/nano12203646.

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Epitaxial strain modifies the physical properties of thin films deposited on single-crystal substrates. In a previous work, we demonstrated that in the case of La2/3Ca1/3MnO3 thin films the strain induced by the substrate can produce the segregation of a non-ferromagnetic layer (NFL) at the top surface of ferromagnetic epitaxial La2/3Ca1/3MnO3 for a critical value of the tetragonality τ, defined as τ = |c − a|a, of τC ≈ 0.024. Although preliminary analysis suggested its antiferromagnetic nature, to date a complete characterization of the magnetic state of such an NFL has not been performed. Here, we present a comprehensive magnetic characterization of the strain-induced segregated NFL. The field-cooled magnetic hysteresis loops exhibit an exchange bias mechanism below T ≈ 80 K, which is well below the Curie temperature of the ferromagnetic La2/3Ca1/3MnO3 layer. The exchange bias and coercive fields decay exponentially with temperature, which is commonly accepted to describe spin-glass (SG) behavior. The signatures of slow dynamics were confirmed by slow spin relaxation over a wide temperature regime. Low-energy muon spectroscopy experiments directly evidence the slowing down of the magnetic moments below ~100 K in the NFL. The experimental results indicate the SG nature of the NFL. This SG state can be understood within the context of the competing ferromagnetic and antiferromagnetic interactions of similar energies.

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Miller, J. D., H. J. Trodahl, M. Al Khalfioui, S. Vézian et B. J. Ruck. « Unlocking perpendicular magnetic anisotropy with Gd substitution in SmN ». Applied Physics Letters 122, n^o 9 (27 février 2023) : 092402. http://dx.doi.org/10.1063/5.0131472.

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A unique bulk-origin perpendicular magnetic anisotropy (PMA) is reported in thin films of the cubic ferromagnetic semiconductor Gd xSm1− xN. PMA behavior is clearly signaled by in-vs-out-of-plane magnetic hysteresis showing out-of-plane remanence of [Formula: see text]% of the saturation magnetization in films with up to 30% Gd. Anomalous Hall effect data show further that the conduction-band spin imbalance shows complete 100% remanence to retain half-metallic conduction even as the out-of-plane applied field is reduced to zero, in stark contrast to the 80% magnetization remanence. The unusual occurrence of PMA in this cubic material is discussed as stabilized by a mix of two in-plane crystal orientations in the epitaxial (111)-oriented films.

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OSHIMA, M., K. ONO, M. MIZUGUCHI, M. YAMADA, J. OKABAYASHI, A. FUJIMORI, H. AKINAGA et M. SHIRAI. « IN-SITU PHOTOELECTRON SPECTROSCOPY OF MAGNETIC DOTS AND MAGNETIC SEMICONDUCTOR NANOSTRUCTURES ». International Journal of Modern Physics B 16, n^o 11n12 (20 mai 2002) : 1681–90. http://dx.doi.org/10.1142/s021797920201110x.

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High resolution angle-resolved photoelectron spectroscopy (ARPES) has been performed on magnetic nanostructures which were in-situ grown hetero-epitaxially on GaAs substrates by low temperature molecular beam epitaxy. Sulfur termination of GaAs surfaces enabled the formation of NiAs-type MnSb dots and zinc-blende (zb) type MnAs dots, showing huge magnetoresistance at RT and half-metallic behavior, respectively. ARPES analysis revealed that the zb-MnAs dots show unique valence band feature with Mn 3d-related peak at about 4 eV of binding energy which is quite similar to (Ga,Mn)As DMS films. Zb-CrAs thin films on GaAs with T c higher than RT are found to show the band dispersion within 2 eV near the Fermi edge, which is in good agreement with the FLAPW calculation. We have also found that (Ga,Cr)As DMS thin films have the similar valence band features to zb-CrAs

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Qiang, B. W., T. Fukasawa, T. Hajiri, T. Ito, T. Hihara et H. Asano. « Magnetic and transport properties of chiral antiferromagnetic Co_2−xPd_xMo₃N thin films ». AIP Advances 13, n^o 2 (1 février 2023) : 025138. http://dx.doi.org/10.1063/9.0000454.

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Hall transport and non-collinear magnetoresistance (NCMR) are studied for a chiral antiferromagnet (AFM) with the filled β-Mn-type structure. Magnetic and transport properties of epitaxial thin films of Co2−xPdxMo3N revealed that, in addition to a canted antiferromagnetic behavior above room temperature, thin films with x = 1.01∼1.38 exhibited a transition to a spin spiral state with a higher magnetic moment below TSR of around 50 K, which was assigned to a spin reorientation transition. The low-temperature phase shows both large anomalous Hall effect (AHE) and topological Hall effect (THE). Upon the transition to the canted AFM phase existing up to room temperature, the large AHE still persists with vanishing THE. The behavior of the Hall transport properties coupled with NCMR signals in the current-perpendicular-to-the plane configuration shows the formation of topological spin textures with locally antiferromagnetic order. The present results open the way for the study of topological antiferromagnetic spin textures, manipulation of their properties, and for future spintronic applications.

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Wang, Wei, Shudong Hu, Zilong Wang, Kaisen Liu, Jinfu Zhang, Simiao Wu, Yuxia Yang, Ning Xia, Wenrui Zhang et Jichun Ye. « Exploring heteroepitaxial growth and electrical properties of α-Ga₂O₃ films on differently oriented sapphire substrates ». Journal of Semiconductors 44, n^o 6 (1 juin 2023) : 062802. http://dx.doi.org/10.1088/1674-4926/44/6/062802.

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Abstract This study explores the epitaxial relationship and electrical properties of α-Ga2O3 thin films deposited on a-plane, m-plane, and r-plane sapphire substrates. We characterize the thin films by X-ray diffraction and Raman spectroscopy, and elucidate thin film epitaxial relationships with the underlying sapphire substrates. The oxygen vacancy concentration of α-Ga2O3 thin films on m-plane and r-plane sapphire substrates are higher than α-Ga2O3 thin film on a-plane sapphire substrates. All three thin films have a high transmission of over 80% in the visible and near-ultraviolet regions, and their optical bandgaps stay around 5.02–5.16 eV. Hall measurements show that the α-Ga2O3 thin film grown on r-plane sapphire has the highest conductivity of 2.71 S/cm, which is at least 90 times higher than the film on a-plane sapphire. A similar orientation-dependence is seen in their activation energy as revealed by temperature-dependent conductivity measurements, with 0.266, 0.079, and 0.075 eV for the film on a-, m-, r-plane, respectively. The origin of the distinct transport behavior of films on differently oriented substrates is suggested to relate with the distinct evolution of oxygen vacancies at differently oriented substrates. This study provides insights for the substrate selection when growing α-Ga2O3 films with tunable transport properties.

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Lee, Jung-Hyuk, Daesu Lee, Tae Won Noh, Pattukkannu Murugavel, Jae Wook Kim, Kee Hoon Kim, Younghun Jo, Myung-Hwa Jung, Jong-Gul Yoon et Jin-Seok Chung. « Formation of hexagonal phase of TbMnO3 thin film and its multiferroic properties ». Journal of Materials Research 22, n^o 8 (août 2007) : 2156–62. http://dx.doi.org/10.1557/jmr.2007.0270.

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TbMnO3 exists in an orthorhombic phase in nature. Recently, we successfully grew TbMnO3 thin films in the hexagonal phase using epitaxial stabilization techniques. In this article, we will show the details of the deposition conditions that allow us to fabricate the hexagonal TbMnO3 films on Pt–Al2O3(0001) substrates. The artificial hexagonal phase can be easily formed above 850 °C, irrespective of the oxygen partial pressure. The hexagonal TbMnO3 films showed ferroelectric properties, which are significantly enhanced compared to those of the orthorhombic TbMnO3 bulk phase. We find interesting anomalies in the magnetic and magnetodielectric properties of the TbMnO3 films at around 45 K, which should be related with the Mn3+ spin reorientation. We also find spin-glass-like behaviors in the magnetic susceptibility, which could be attributed to the geometric frustration of antiferromagnetically coupled Mn spins with an edge-sharing triangular lattice. This work shows details of the growth and properties of hexagonal TbMnO3 films.

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Orna, Julia, Luis Morellón, Pedro Algarabel, José M. De Teresa, Amalio Fernández-Pacheco, Gala Simón, Cesar Magen, José A. Pardo et M. Ricardo Ibarra. « Fe₃O₄ Epitaxial Thin Films and Heterostructures : Magnetotransport and Magnetic Properties ». Advances in Science and Technology 67 (octobre 2010) : 82–91. http://dx.doi.org/10.4028/www.scientific.net/ast.67.82.

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In this article, we review our recent research on Fe3O4 epitaxial thin films and Fe3O4/MgO/Fe epitaxial heterostructures. More specifically, we report on the magnetotransport properties of Fe3O4 epitaxial films in a wide range of film thicknesses and temperatures, focusing on the anomalous, planar and ordinary Hall effects. We also summarize our insight on the origin of the enhanced magnetic moment found in ultra-thin magnetite films (thickness t < 5 nm). Finally, our work on the growth, and structural and magnetic characterization of heteroepitaxial Fe3O4/MgO/Fe trilayers is presented.

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Yan, Li, Yu Wang, Jiefang Li, Alexander Pyatakov et D. Viehland. « Nanogrowth twins and abnormal magnetic behavior in CoFe2O4 epitaxial thin films ». Journal of Applied Physics 104, n^o 12 (15 décembre 2008) : 123910. http://dx.doi.org/10.1063/1.3033371.

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Soriano, S., K. Dumesnil, C. Dufour, M. Hennion, J. A. Borchers et Ph Mangin. « Clamping effect on the magnetic behavior of europium epitaxial thin films ». Journal of Applied Physics 97, n^o 10 (15 mai 2005) : 10K111. http://dx.doi.org/10.1063/1.1854437.

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Tran, Thi Toan, Thi Hoa Vu, Anh Tuan Pham, Thi Huong Nguyen, Van Quang Nguyen, Chanyong Hwang et Sunglae Cho. « MBE growth and abnormal magnetic behaviors of epitaxial Fe_100−xGa_x on SrTiO₃ ». AIP Advances 13, n^o 3 (1 mars 2023) : 035334. http://dx.doi.org/10.1063/5.0136344.

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Here, we present the magnetic behaviors of disordered bcc α-Fe phase Fe100−xGax (x = 10, 20, and 30) thin films grown on a SrTiO3 substrate using molecular beam epitaxy. With the Ga content increasing from 10% to 30%, the saturation magnetization decreased from 1575 to 991 emu/cm3 while the coercivity increased from 23 to 197 Oe. A two-step-hysteresis loop was observed in all films. Specifically, the hysteresis loop of the film with 10% Ga concentration reveals an obvious kink. Magneto-optical Kerr images confirmed the abnormal magnetic domain switching in the films, which is due to the appearance of perpendicular domains under external magnetic field.

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Zając, M., K. Freindl, T. Ślęzak, M. Ślęzak, N. Spiridis, D. Wilgocka-Ślęzak et J. Korecki. « Electronic and magnetic properties of ultra-thin epitaxial magnetite films on MgO(001) ». Thin Solid Films 519, n^o 16 (juin 2011) : 5588–95. http://dx.doi.org/10.1016/j.tsf.2011.03.037.

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Wu, Chunfang, Wenzhe Guo, Congmian Zhen, Hongru Wang, Guoke Li, Li Ma et Denglu Hou. « Short-range magnetic order and electrical behavior in epitaxial NiCo2O4 thin films ». Journal of Applied Physics 126, n^o 4 (28 juillet 2019) : 043901. http://dx.doi.org/10.1063/1.5100675.

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Mercaldo, Lucia V., Vladimir V. Talanov, Steven M. Anlage, Carmine Attanasio et Luigi Maritato. « Microwave Electrodynamics of low TC and high TC Systems with Coexisting Superconductivity and Magnetism ». International Journal of Modern Physics B 14, n^o 25n27 (30 octobre 2000) : 2920–25. http://dx.doi.org/10.1142/s0217979200003101.

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We investigate the microwave electrodynamics of both artificial low T C superconducting/magnetic (S/M) layered structures and high T C cuprates. In particular we focus on Nb/CuMn (superconducting/spin-glass) bilayers, and on GbBa 2 Cu 3 O 7-δ (GBCO) thin films, which show coexistence of superconductivity and long range ordered antiferromagnetism below T N = 2.2 K . In both cases we are interested in the influence of magnetism on superconducivity. Moreover, in the GBCO case, we want to shed light on the problem of the determination of the pairing symmetry in the cuprates. First we show surface impedance data at 10 GHz on Nb/CuMn bilayers. We extract information about the induced order parameter in the magnetic layer and we compare it with the exotic behavior predicted for S/M proximity systems. Then we present microwave surface impedance data at three different frequencies on GBCO c-axis oriented epitaxial thin films. Both the resistance and the reactance data on GBCO show an unusual low temperature behavior, mainly due to change in magnetic permeability. This result indicates that the paramagnetism of the rare-earth ions has to be taken into account when extracting the superconducting penetration depth as a function of temperature, and thus determining the pairing state symmetry of the cuprates.

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Yun-Ping, Wang, Zhang Dian-Lin et Zhao Bai-Ru. « Anomalous Hall Effect of YBa2Cu3O7-δ in the Low-Magnetic-Field Limit ». Modern Physics Letters B 12, n^o 18 (10 août 1998) : 719–26. http://dx.doi.org/10.1142/s0217984998000846.

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The Hall effect of YBa 2 Cu 3 O 7-δ epitaxial films in the vicinity of superconducting transition was studied under ultra low magnetic fields down to 10-3 T where some field-induced extrinsic effects, such as the reduction and broadening of the transition temperature and the enhancement of fluctuation, can be neglected. The Hall sign reversal was still observed down to the lowest field we arrived, which shows that any mechanism connected with above mentioned extrinsic changes cannot be responsible for the effect. The Hall resistivity ρxy, Hall angle tan α and Hall conductivity σxy are all simply proportional to the magnetic field, resembling the behaviors of the ordinary Hall effect in the low-magnetic-field limit. The temperature range with observable negative Hall resistivity coincides with the critical fluctuation region. These behaviors shows that the negative Hall effect cannot be understood in the picture of flux flow.

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ILONCA, G., A. V. POP, G. STIUFIUC, C. LUNG et R. STIUFIUC. « ACTIVATION ENERGY OF Bi2Sr2Ca(Cu1-xFex)2O8+d THIN FILMS ». Modern Physics Letters B 15, n^o 22 (20 septembre 2001) : 959–64. http://dx.doi.org/10.1142/s0217984901002956.

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The scaling behavior of the effective activation energy U(T,H) of epitaxial c-axis oriented Bi 2 Sr 2 Ca ( Cu 1-x Fe x)2 O 8+d thin films with 0 ≤ x ≤ 0.02 has been studied as a function of temperature and magnetic field. It has been found that the activation energy scales as U(H,T) = U0(1 - t)mHn with exponent m = 1.15 ± 0.03 and n = -1/2. The field and temperature dependence of the activation energy, as well as its overall magnitude is consistent with a model in which U(T,H) arises from plastic deformations of viscous flux liquid above the vortex-glass transition temperature.

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Tanabe, Iori, Haseeb Kazi, Yuan Cao, Jack L. Rodenburg, Takashi Komesu, Bin Dong, Frank L. Pasquale, M. Sky Driver, Jeffry A. Kelber et Peter A. Dowben. « Strain induced super-paramagnetism in Cr2O3 in the ultra thin film limit ». MRS Proceedings 1729 (2015) : 79–83. http://dx.doi.org/10.1557/opl.2015.5.

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ABSTRACTUltra thin films of chromia (Cr2O3), less than 3 nm thick, grown epitaxial on α-Al2O3 (sapphire), and are thus compressively strained in-plane. The resulting films show evidence of some magnetic ordering above the Néel temperature of chromia (307 K). The observed higher temperature hysteresis effect observed are very likely a strain effect, and not associated with the typical antiferromagnetic ordering expected of chromia.

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de Melo, C., C. Guillemard, A. M. Friedel, V. Palin, J. C. Rojas-Sánchez, S. Petit-Watelot et S. Andrieu. « Unveiling transport properties of Co2MnSi Heusler epitaxial thin films with ultra-low magnetic damping ». Applied Materials Today 25 (décembre 2021) : 101174. http://dx.doi.org/10.1016/j.apmt.2021.101174.

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Chen, C. L., Z. Zhang, H. Feng, G. P. Luo, S. Y. Chen, A. Heilman, W. K. Chu et al. « Epitaxial behavior and interface structures of BSTO thin films ». Integrated Ferroelectrics 28, n^o 1-4 (mars 2000) : 237–46. http://dx.doi.org/10.1080/10584580008222235.

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Reith, Timothy, J. M. Shaw et C. M. Falco. « Effect of very thin Cr films on the magnetic behavior of epitaxial Co ». Journal of Applied Physics 99, n^o 8 (15 avril 2006) : 08N506. http://dx.doi.org/10.1063/1.2164434.

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Le Marrec, F., A. Demuer, D. Jaccard, J. M. Triscone, M. K. Lee et C. B. Eom. « Magnetic behavior of epitaxial SrRuO3 thin films under pressure up to 23 GPa ». Applied Physics Letters 80, n^o 13 (avril 2002) : 2338–40. http://dx.doi.org/10.1063/1.1459484.

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Dziwoki, Adam, Bohdana Blyzniuk, Kinga Freindl, Ewa Madej, Ewa Młyńczak, Dorota Wilgocka-Ślęzak, Józef Korecki et Nika Spiridis. « Magnetic-Field-Assisted Molecular Beam Epitaxy : Engineering of Fe3O4 Ultrathin Films on MgO(111) ». Materials 16, n^o 4 (10 février 2023) : 1485. http://dx.doi.org/10.3390/ma16041485.

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Molecular beam epitaxy is widely used for engineering low-dimensional materials. Here, we present a novel extension of the capabilities of this method by assisting epitaxial growth with the presence of an external magnetic field (MF). MF-assisted epitaxial growth was implemented under ultra-high vacuum conditions thanks to specialized sample holders for generating in-plane or out-of-plane MF and dedicated manipulator stations with heating and cooling options. The significant impact of MF on the magnetic properties was shown for ultra-thin epitaxial magnetite films grown on MgO(111). Using in situ and ex situ characterization methods, scanning tunneling microscopy, conversion electron Mössbauer spectroscopy, and the magneto-optic Kerr effect, we showed that the in-plane MF applied during the reactive deposition of 10 nm Fe3O4(111)/MgO(111) heterostructures influenced the growth morphology of the magnetite films, which affects both in-plane and out-of-plane characteristics of the magnetization process. The observed changes are explained in terms of modification of the effective magnetic anisotropy.

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Šutara, F., M. Cabala, L. Sedláček, T. Skála, M. Škoda, V. Matolín, K. C. Prince et V. Cháb. « Epitaxial growth of continuous CeO2(111) ultra-thin films on Cu(111) ». Thin Solid Films 516, n^o 18 (juillet 2008) : 6120–24. http://dx.doi.org/10.1016/j.tsf.2007.11.013.

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Linker, G., R. Smithey, J. Geerk, F. Ratzel, R. Schneider et A. Zaitsev. « The growth of ultra-thin epitaxial CeO2 films on r-plane sapphire ». Thin Solid Films 471, n^o 1-2 (janvier 2005) : 320–27. http://dx.doi.org/10.1016/j.tsf.2004.05.126.

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Moog, E., et S. Bader. « Magneto-optical studies of ultra-thin epitaxial films of fcc Fe on Cu ». IEEE Transactions on Magnetics 23, n^o 5 (septembre 1987) : 3202–4. http://dx.doi.org/10.1109/tmag.1987.1065250.

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Gao, J., et F. X. Hu. « The abnormal electroresistance behavior observed in epitaxial La0.8Ca0.2MnO3 thin films ». Thin Solid Films 515, n^o 2 (octobre 2006) : 555–58. http://dx.doi.org/10.1016/j.tsf.2005.12.294.

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Jaren, S., E. du Trémolet de Lacheisserie, D. Givord et C. Meyer. « Pulsed laser deposition epitaxial growth and magnetic properties of TbCo2 and TbFe2 ultra-thin films ». Journal of Magnetism and Magnetic Materials 165, n^o 1-3 (janvier 1997) : 172–75. http://dx.doi.org/10.1016/s0304-8853(96)00498-2.

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Goyhenex, Christine, R. V. P. Montsouka, Mirosław Kozłowski et Veronique Pierron-Bohnes. « Interdiffusion of Two L1₀Phases without Long-Range Order Decrease : Experiments and Molecular Dynamics Simulations ». Solid State Phenomena 129 (novembre 2007) : 59–66. http://dx.doi.org/10.4028/www.scientific.net/ssp.129.59.

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The L10 ordered MPt(001) thin films (M = Fe or Co) are very interesting for perpendicular recording due to their magnetic anisotropy and magneto-optical behaviours. Epitaxial L10-ordered NiPt(001) / FePt(001) bi-layers were co-deposited on MgO(100) substrates by MBE. The L10 order parameter is high with the concentration modulation along the growth direction. Some FeNiPt2(001) thin films were obtained by interdiffusion of the bilayers. The long-range-order parameter is conserved after interdiffusion (S = 0.75 ± 0.06), which can be explained by different mechanisms: a second-neighbour jump, a six-jump cycle, an anti-structural bridge mechanism or an antisite-pair elimination and creation mechanism, a double vacancy or a triple defect diffusion mechanism. Quenched molecular dynamics calculations in the frame of the second moment approximation of the tight binding method have been performed to obtain the energetic paths of the different mechanisms. The secondneighbour vacancy jump, the simultaneous jumps of bivacancies and the triple defect mechanisms can be ruled out for energetic reasons.

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WECKHUYSEN, L., J. VANACKEN, P. WAGNER, K. Q. RUAN, I. GORDON, V. V. MOSHCHALKOV et Y. BRUYNSERAEDE. « HIGH-FIELD MAGNETOTRANSPORT OF EPITAXIAL LA2-XSRXCUO4 THIN FILMS IN THE REGIME OF LOW SR-DOPING ». International Journal of Modern Physics B 14, n^o 29n31 (20 décembre 2000) : 3747–52. http://dx.doi.org/10.1142/s0217979200004295.

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High temperature superconductors have an unusual temperature (T) — doping (x) phase diagram, in which both antiferromagnetism and superconductivity occur. The spin gap and the superconducting gap are the two essential features of the T(x) plane which evolve with doping. A material allowing investigating the T-x plane in detail, from the underdoped (x<0.15) to the overdoped (x>0.15) regime, is the La 2- x Sr x CuO 4 superconductor. The temperature dependence of the resistivity strongly depends on the substitution ratio x. Overdoped films show metallic behavior, meaning that ρ(T) is linear above 100 K, while it saturates for lower temperatures. This saturation persists below Tc, when superconductivity is suppressed by sufficiently high pulsed magnetic fields. From the slightly overdoped (0.2<x) down to the strongly underdoped regime (x~0.03) we observe, instead of saturation, a ρ(T) dependence with logarithmic divergence in the field-induced normal state at T→0. For underdoped films (x<0.1) a superlinear ρ(T) behavior develops at intermediate temperatures (50 K <T<200 K ), indicating the opening of the spin gap.

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