398 research outputs found
Influence of tetragonal distortion on the magnetic and electronic properties of the Heusler compound Co2TiSn from first principles
Using the full potential linearized augmented plane wave plus local orbitals
method we determine ab-initio the lattice parameters of tetragonally distorted
Co2TiSn in the L21 structure. The tetragonal lattice parameter c is determined
as a function of the lattice parameter a by energy minimization. The change in
total energy is found to be only a few with respect to room
temperature. The spin polarizations as well as the magnetizations are stable
against small lattice distortions. It is shown, that the volume is not constant
upon distortion and that the volume change is related with significant changes
in the magnetization and the gap energy.Comment: 3 pages, 4 figure
Ab initio prediction of ferrimagnetism, exchange interactions and Curie temperatures in Mn2TiZ Heusler compounds
The Heusler compounds MnTiZ (Z = Al, Ga, In, Si, Ge, Sn, P, As, Sb) are
of large interest due to their potential ferrimagnetic properties and high spin
polarization. Here, we present calculations of the structural and magnetic
properties of these materials. Their magnetic moment follows the Slater-Pauling
rule . None of them is actually a perfect half-metallic
ferrimagnet, but some exhibit more than 90% spin polarization and Curie
temperatures well above room temperature. The exchange interactions are
complex, direct and indirect exchange contributions are identified. The Curie
temperature scales with the total magnetic moment, and it has a positive
pressure dependence. The role of the Z element is investigated: it influences
the properties of the compounds mainly via its valence electron number and its
atomic radius, which determines the lattice parameter. Based on these results,
MnTiSi, MnTiGe, and MnTiSn are proposed as candidates for
spintronic applications.Comment: 13 pages, 6 figure
Spin transfer torque oscillator based on asymmetric magnetic tunnel junctions
We present a study of the spin transfer torque oscillator based on
CoFeB/MgO/CoFeB asymmetric magnetic tunnel junctions. We observe microwave
precession in junctions with different thickness of the free magnetization
layer. Taking advantage of the ferromagnetic interlayer exchange coupling
between the free and reference layer in the MTJ and perpendicular interface
anisotropy in thin CoFeB electrode we demonstrate the nanometer scale device
that can generate high frequency signal without external magnetic field
applied. The amplitude of the oscillation exceeds 10 nV/Hz^0.5 at 1.5 GHz.Comment: 4 pages, 4 figures, to be submitted to Applied Physics Letter
Percolation threshold and mean grain size in AlxSi1-x thin films
Reiss G, Vancea J, Hoffmann H. Percolation threshold and mean grain size in AlxSi1-x thin films. Journal of Physics, C: Solid State Physics. 1985;18(21):L657-L660.We determined the critical composition xc of the percolation threshold in polycrystalline AIxSi1-x thin films with a new method, using structural arguments only. The result xc = (0.55 + - 0.05) agrees with the results of the commonly used methods. Moreover, our model explains the wide spread of experimental values of xc as reported in the literature
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