Influence of the interface morphology on the magnetization of Magnetic/Non-Magnetic (Fe/Cu) multilayers: a Monte Carlo investigation

A Monte Carlo investigation was used to study the magnetization of a Heisenberg multilayers system. Our model consists of an alternate staking of Magnetic and Non-Magnetic layers (M/NM) with disordered interfaces. The results indicate that the magnetization of multilayers M/NM depends on the atomic composition, the interface morphology and the exchange interactions at the interface.A Monte Carlo investigation was used to study the magnetization of a Heisenberg multilayers system. Our model consists of an alternate staking of Magnetic and Non-Magnetic layers (M/NM) with disordered interfaces. The results indicate that the magnetization of multilayers M/NM depends on the atomic composition, the interface morphology and the exchange interactions at the interface

Mössbauer study and Monte Carlo simulations of the hyperfine field distribution in Magnetic/Non-Magnetic (M/NM) multilayers

Using a Monte Carlo numerical method, we perform a complementary analysis of the hyperfine field distribution in Magnetic/Non-Magnetic (M=Fe/NM=Cu) multilayers and a comparison with Mössbauer experiment results of [Fe(40)=Cu(20)]20 multilayers. From differing relaxation rates for spins with few near neighbor spins and particularly those located at the interface, the Mössbauer result can be simulated. Our model consists of an alternate stacking of magnetic and non-magnetic layers (MnM/NMnNM) with disordered interface. The simulation results confirm that the concentration of interface alloys (M1-xNMx) and magnetic layer thickness modify systemically the magnetization distribution in the M/NM multilayers. The result is in agreement with Mössbauer experimental analysis

THE IRON SPIN TEXTURE IN ANNEALED AMORPHOUS Fe/Tb MULTI-LAYERS

Fe/Tb multilayers have been obtained by vacuum evaporation with Tb-layer thickness fixed to 40Å and amorphous Fe-layer thickness fixed to 19Å. 57Fe-Mössbauer spectrometry was used to obtain information on the structure and the spin texture of the multilayers before and after annealing at 530K for different durations of the annealing. The Mössbauer results indicate that the Perpendicular Magnetic Anisotropy (PMA) was stabilised and reinforced after annealing.Fe/Tb multilayers have been obtained by vacuum evaporation with Tb-layer thickness fixed to 40Å and amorphous Fe-layer thickness fixed to 19Å. 57Fe-Mössbauer spectrometry was used to obtain information on the structure and the spin texture of the multilayers before and after annealing at 530K for different durations of the annealing. The Mössbauer results indicate that the Perpendicular Magnetic Anisotropy (PMA) was stabilised and reinforced after annealing

Atomic scale simulation of epitaxial growth: Cases of GaAs/GaAs and CdTe/GaAs

We present a kinetic Monte Carlo model describing the growth by molecular beam epitaxy (MBE) of semiconductor compounds and including a local photoemission model with reflection high-energy electron diffraction (RHEED) intensity for comparison. We investigate the cases of both homoepitaxial and heteroepitaxial growth. The valence force field approximation is used for the strain energy calculations in mismatched thin films In homoepitaxial growth of GaAs, we have study the variations of photoemission current and RHEED intensity and examined the GaAs morphology. In high lattice mismatch heteroepitaxial growth (CdTe/GaAs), we have shown the formation of grooves corresponding to (111) facets, precursor to the formation of misfit defects.We present a kinetic Monte Carlo model describing the growth by molecular beam epitaxy (MBE) of semiconductor compounds and including a local photoemission model with reflection high-energy electron diffraction (RHEED) intensity for comparison. We investigate the cases of both homoepitaxial and heteroepitaxial growth. The valence force field approximation is used for the strain energy calculations in mismatched thin films In homoepitaxial growth of GaAs, we have study the variations of photoemission current and RHEED intensity and examined the GaAs morphology. In high lattice mismatch heteroepitaxial growth (CdTe/GaAs), we have shown the formation of grooves corresponding to (111) facets, precursor to the formation of misfit defects

Magnetic Behaviour of Disordered Ising Ferrimagnet in High Magnetic Field

The magnetic behaviour of a disordered ferrimagnetic system Ap B1-p where both A and B represent the magnetic atoms with respective spin SA = 1/2 and SB = 1 in presence of high magnetic field is treated theoretically.Assuming the magnetic interaction can be described through Ising Hamiltonian the approximate free energy is obtained using the cluster-variational method. The field dependence of the magnetization is then obtained for different concentration p and exchange parameters (JAA, JBB and JAB). For p = 0.5,the magnetization M in ferrimagnetic state and in absence of compensation temperature Tcm vanishes at TC.Field induced reversal of M is found at switching temperature TS (<TC) which is decreasing function of field H.A maximum in M is found above TS and the maximum value of M increases with field.In ferrimagnetic state M increases almost linearly at high H region. For system with large ferromagnetic JAA,the compensation temperature Tcm is increasing function of JBB and JAB .The decrease in compensation temperature is linear at small field and tends to saturate at higher field.The sharpness of the magnetization reversal is increased with H.For fully compensated state of the system with p = 2/3,the magnetization in presence of H also exhibits switching behaviour at TS .For p = 0.2 the field induced reversal of magnetization occurs more sharply.The orientational switching of the sublattice magnetization MA and MB with field increases the Zeeman energy and is the origin of magnetization reversal at TsComment: 12 pages,9 Figure

Guide d'onde coplanaire à base de nanofils de CoFe2O4

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A high magnetic field sensor based on magnetic tunnel junctions

We used an in-plane magnetized electrode and a perpendicular to film plane magnetized multilayer electrode in a magnetic tunnel junction to generate the active part of a magnetic field sensor able to measure large fields. When the applied field is normal to the junction surface, the magnetization of the multilayer electrode is fixed while the moment of the in-plane magnetized electrode rotates towards the applied field. This generates a linear variation of tunnel junction resistance with the applied field. The use of tunnel junctions with all their known advantages makes this structure attractive for measuring large magnetic fields, of up to several kG

Structural, morphologic and magnetic properties of Pr0.6La0.1Ca0.3Mn1−xFexO3 (0≤x≤0.3) perovskite nanopowder

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Effect of the annealing temperature on the structural and magnetic behaviors of 0.875La 0.6 Ca 0.4 MnO 3 /0.125La 0.6 Sr 0.4 MnO 3 composition

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Investigation of relaxor and diffuse dielectric phase transitions of Ba1-XBixTi0.8Fe0·2O3 materials

Different doping elements have been used to enhance the dielectric properties of BaTiO3 ceramic. In this work, the effect of substitution of Ba by Bi in A site and Ti by Fe in B site on structural, dielectric and electrical properties of Ba1-xBixTi0.80Fe0·20O3 ceramics at (x = 0.00, 0.05, 0.10 and 0.15) was investigated by X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy (SEM), Mössbauer spectroscopy as well as dielectric measurements. The Rietveld refinement results revealed that the prepared compounds crystallize in both tetragonal (P4mm) and hexagonal (P63/mmc) phases for x = 0.00 and 0.05 while at x = 0.10 and 0.15, the hexagonal phase disappears and only the tetragonal phase is fitted. The Raman spectra confirmed the disappearance of hexagonal phase in benefit of tetragonal phase as the Bi3+ substitution increases. Based on Mössbauer analyses results, all the samples are in paramagnetic state at room temperature and the Fe is oxidized under Fe3+ without the presence of Fe2+ or Fe4+ ions. The dielectric measurements as function of temperature are studied and tree broad and relaxor phase transitions were detected: from rhombohedral to orthorhombic phase TR-O and to tetragonal ferroelectric phase TO-T then to cubic paraelectric phase Tm. These phase transitions were displaced to the lower temperature with increasing of Bi3+ substitution. The values of ε′r increase gradually with increasing of Bi3+contents which confirmed the enhancement of dielectric properties of BaTi0·80Fe0·20O3 by Bi substitution on Ba site. The diffuse phase transitions were described by fitting the modified Uchino relation. The Cole–Cole analyses showed that both the grain and grain boundaries resistivity values are higher for Bi3+ substituted samples which are responsible to the dielectric properties improvement