Unravelling the effect of SrTiO3 antiferrodistortive phase transition on the magnetic properties of La0.7Sr0.3MnO3 thin films (original) (raw)
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Nanomaterials, 2021
Epitaxial La0.7Sr0.3MnO3 films with different thicknesses (9–90 nm) were deposited on SrTiO3 (0 0 1) substrates by pulsed laser deposition. The films have been investigated with respect to morpho-structural, magnetic, and magneto-transport properties, which have been proven to be thickness dependent. Magnetic contributions with different switching mechanisms were evidenced, depending on the perovskite film thickness. The Curie temperature increases with the film thickness. In addition, colossal magnetoresistance effects of up to 29% above room temperature were evidenced and discussed in respect to the magnetic behavior and film thickness.
Journal of Applied Physics, 2008
La 0.60 Sr 0.40 MnO 3 (LSMO) thin films of varying thickness from 12 to 55 nm were deposited using the pulsed-laser deposition technique onto single-crystalline SrTiO3 (STO) and STO-buffered Si substrates. The Tc of LSMO films grown on STO-buffered Si substrates decreases faster than films directly grown on STO with decreasing film thickness. The LSMO/STO film with thickness of 55 nm shows Tc at about 360 K, which is close to the bulk value, whereas Tc LSMO film on STO-buffered Si film of similar thickness is reduced to 320 K. This difference is attributed to the strain and interfacial disorders in LSMO film on STO/Si. The film surface morphology is influenced by the film thickness. Oxygenation of LSMO films on STO-buffered Si affects the Tc minimally but improved the overall magnetization of the films due to better oxygenation, which is also the case for postannealing the sample at elevated temperatures. The thermomagnetic history effects observed in LSMO films of STO-buffered Si i...
Epitaxial thin films of half-metallic oxide La0.7Sr0.3MnO3 (LSMO) have been grown in two crystalline orientations, one with the c-axis out-of-plane, the (001) orientation, and one with the c-axis in-plane, the (110) orientation. For the (110) oriented growth, there is no polar discontinuity at the substrate–film interface and hence no dead layer formation, which improves ferromagnetic interaction in the LSMO, making it highly attractive for spintronic applications. In our experiments, with x-ray diffraction, x-ray photoelectron spectroscopy and magnetic measurements, we have demonstrated that in the (110) oriented LSMO the lattice is more relaxed, leading to less deformation of electronic density around the La atom or in the MnO6 octahedra. This improved crystal and electronic structure improves the ferromagnetic properties of the films, making the Curie temperature higher by almost 15 K, which is of potential interest for spintronics. However, substrate strain induced magnetic anisotropy causes domain formation with out-of-plane components in these films, which poses some concern for practical spintronic devices.
Journal of Nanoparticle Research, 2011
Nearly 50-nm thick La 0.7 Sr 0.3 MnO 3 (LSMO) films were grown on Si substrates using molecular beam epitaxy on (001) Si substrates overlayered by a 20 nm thick SrTiO 3 (STO) or by a 20 nm thick CaTiO 3 (CTO) film. In addition, a reference LSMO film was directly deposited on a (001) STO substrate by pulsed laser deposition. For all the samples, X-ray diffraction revealed an excellent epitaxy of the LSMO film and small mosaicity around (001), with in-plane [100] and [010] cubic axes. The LSMO/CTO films are in-plane compressed while the LSMO/STO ones are in-plane extended. The temperature dependence of their static magnetic properties was studied using a SQUID, showing a Curie temperature overpassing 315 K for all the samples. Hysteresis loops performed at room temperature (294 K) with the help of a vibrating sample magnetometer (VSM) are also discussed. At 294 K Micro-strip ferromagnetic resonance (MS-FMR) was used to investigate the dynamic magnetic properties. It allows concluding to a strong anisotropy perpendicular to the films and to a weak fourfold in-plane anisotropy with easy axes along the [110] and [1 " 10] directions. Their values strongly depend on the studied sample and are presumably related to the strains suffered by the films.
Journal of Alloys and Compounds, 2012
Colossal magnetoresistive manganite La 0.7 Sr 0.3 MnO 3 (LSMO) films were prepared by pulsed laser deposition on three different single crystal substrates using different deposition parameters. Characterizations of their surface morphologies, structural, magnetic and magneto-transport properties show that films on MgO single crystal substrates contain higher amount of structural defects compared to those on SrTiO 3 (STO) and NdGaO 3 (NGO) substrates. Low deposition rate and thicker films give rise to polycrystallinity and grain boundaries. The films on MgO substrate showed a broad paramagnetic (PM) to ferromagnetic (FM) transition accompanied with metal -insulator transition (MIT) much below their Curie temperature (T C ) indicating growth of strained structures due to large lattice mismatch (9%) between the substrate and the film. The deposited films on STO and NGO show least effect of substrate induced strain exhibiting sharper PM-FM transition and metallic behavior below T C . The magnetoresistance (MR) † Corresponding author e-mail: sayani.majumdar@utu.fi, Phone: +358 2 3336240, Fax: +358 2 3335070
Magnetoresistance anisotropy of ultrathin epitaxial La0.83Sr0.17MnO3 films
Journal of Applied Physics, 2017
We present the study of temperature dependence of resistivity (ρ), magnetoresistance (MR), and magnetoresistance anisotropy (AMR) of thin epitaxial La0.83Sr0.17MnO3 films. The films with thickness from 4 nm to 140 nm were grown on an NdGaO3 (001) substrate by a pulsed injection metal organic chemical vapor deposition technique. We demonstrate that the resistivity of these films significantly increases and the temperature Tm of the resistivity maximum in ρ(T) dependence decreases with the decrease of film thickness. The anisotropy of ρ(T) dependence with respect to the electrical current direction along the [100] or [010] crystallographic axis of the film is found for ultrathin films (4–8 nm) at temperatures close to Tm. Both MR and AMR, measured in magnetic fields up to 0.7 T applied in the film plane parallel and perpendicular to the current direction, have shown strong dependence on the film thickness. It was also found that the anisotropy of magnetoresistance could change its sig...
Journal of Physics D: Applied Physics
The crystal structural quality and the strain induced by the substrate strictly impose the magnetic and transport properties of La 0.67 Sr 0.33 MnO 3 (LSMO) films. In particular, the magnetic anisotropy (MA) of epitaxial LSMO can be finely tuned by varying its thickness and by choosing single crystal substrates with suitable lattice mismatch with the film. Here, we have deposited LSMO films with thicknesses in the 12-50 nm range by pulsed laser deposition on different single crystal substrates inducing either compressive or tensile in-plane strain on the manganites. The epitaxial quality of films was quantified by ω-scans around (002) peak with full-width half-maximum (FWHM) values as low as 0.08° for films on the nearly matched NGO (110) substrate to 1.4° films on high mismatched MgO (001) substrate. As the epitaxial strain in thin-film increases, a significant reduction in metal-insulation transition (MIT) temperature (T p) was observed. The magnetic properties of the films probed by Kerr magnetometry show that the symmetry of the room temperature MA varies significantly as a function of both strain and thickness. Specifically, we observed pure uniaxial MA on NGO (110) and pure biaxial MA on STO buffered MgO (001), whereas a spin reorientation from uniaxial in-plane to out-of-plane on LSAT (001) and uniaxial to nearly isotropic in-plane on STO (001) substrate as the film thickness is increased. We provide an efficient tool to tune the MA according to the specific spintronic application targeted.
Magnetization reversal and magnetoresistance in vicinal La0.7Sr0.3MnO3 thin films
Magnetic hysteresis of ½CoFe=Au=Co=Au N multilayers displaying giant magnetoresistance was investigated. It is shown that an effective coupling between the neighboring magnetic layers can be modified by the changes of the structure of the multilayers. It is shown, too, that this coupling is influenced by temperature. Some of the observed dependencies are explained on the basis of micromagnetic simulations.
Journal of Physics D: Applied Physics, 2016
The suitability of a particular material for use in magnetic devices is determined by the process of magnetization reversal/relaxation, which in turn depends on the magnetic anisotropy. Therefore, designing new ways to control magnetic anisotropy in technologically important materials is highly desirable. Here we show that magnetic anisotropy of epitaxial thin-films of half-metallic ferromagnet La0.7Sr0.3MnO3 (LSMO) is determined by the proximity to thermodynamic equilibrium conditions during growth. We performed a series of X-ray diffraction and ferromagnetic resonance (FMR) experiments in two different sets of samples: the first corresponds to LSMO thin-films deposited under tensile strain on (001) SrTiO3 by Pulsed Laser Deposition (PLD; far from thermodynamic equilibrium); the second were deposited by a slow Chemical Solution Deposition (CSD) method, under quasi-equilibrium conditions. Thin films prepared by PLD show a in-plane cubic anisotropy with an overimposed uniaxial term. A large anisotropy constant perpendicular to the film plane was also observed in these films. However, the uniaxial anisotropy is completely suppressed in the CSD films. The out of plane anisotropy is also reduced, resulting in a much stronger in plane cubic anisotropy in the chemically synthesized films. This change is due to a different rotation pattern of MnO6 octahedra to accomodate epitaxial strain, which depends not only on the amount of tensile stress imposed by the STO substrate, but also on the growth conditions. Our results demonstrate that the nature and magnitude of the magnetic anisotropy in LSMO can be tuned by the thermodynamic parameters during thin-film deposition.