36 research outputs found
Magnetic and transport properties of tetragonal- or cubic-Heusler-type Co-substituted Mn-Ga epitaxial thin films
The composition dependence of the structural, magnetic, and transport
properties of epitaxially grown Mn-Co-Ga films were investigated. The crystal
structure was observed to change from tetragonal to cubic as the Co content was
increased. In terms of the dependence of saturation magnetization on the Co
content, relatively small value was obtained for the
MnCoGa film at a large {\it K} value of 9.2
Merg/cm. Electrical resistivity of Mn-Co-Ga films was larger than that of
pure Mn-Ga film. The maximum value of the resistivity was 490 cm for
MnCoGa film. The high resistivity of Mn-Co-Ga might be
due to the presence of localized electron states in the films due to chemical
disordering caused by the Co substitution.Comment: 3 pages, 5 figures. The article has been submitted to the Journal of
Applied Physics as a Proceedings for the 12th Joint MMM/INTERMAG conferenc
Magnetic dichroism study on MnCoGa thin film using a combination of X-ray absorption and photoemission spectroscopy
Using circularly polarised radiation and a combination of bulk-sensitive hard
X-ray photoelectron spectroscopy and X-ray-absorption spectroscopy (XAS) we
studied the electronic and magnetic structure of epitaxial
MnCoGa thin films. Spin resolved Bloch spectral functions,
density of states as well as charge and magnetisation densities were
investigated by a first-principles analysis of full potential, fully
relativistic Korringa--Kohn--Rostoker calculations of the electronic structure.
The valence states were experimentally investigated by using linear dichroism
in the angular distribution and comparing the results to spin-resolved
densities of states. The linear dichroism in the valence band enabled a
symmetry analysis of the contributing states. The spectra were in good
agreement with the theoretical partial density of states. The element-specific,
spin-resolved, unoccupied densities of states for Co and Mn were analysed by
using XAS and X-ray magnetic circular dichroism (XMCD) at the edges.
The spectra were influenced by strong correlation effects. XMCD was used to
extract the site resolved magnetic moments. The experimental values of and agree very well with the
calculated magnetic moments. Magnetic circular dichroism in angle-resolved
photoelectron spectroscopy at the Mn and Co core level exhibited a
pronounced magnetic dichroism and confirmed the localised character of the Mn
valence states
Perpendicularly magnetized Mn-Co-Ga-based thin films with high coercive field
MnCoGa epitaxial thin films were grown on MgO substrates by
magnetron co-sputtering. Structures were tetragonal or cubic depending on Co
content. Composition dependence of saturation magnetization and uniaxial
magnetic anisotropy of the films were investigated. A high (1.2 MJ
m) was achieved for the MnCoGa film with the
magnetic moment 0.84. Valence band spectra were obtained by hard X-ray
photoelectron spectroscopy. Sharp peaks in the cubic case, which were absent in
the tetragonal case, prove that a van Hove singularity causes a band
Jahn-Teller effect with tetragonal distortion. Observations agree well with the
first-principles calculations
Fabrication of MgO-based magnetic tunnel junctions with CoCrPt perpendicularly magnetized electrodes
Fabrication of magnetic tunnel junctions with a metastable bcc Co3Mn disordered alloy as a bottom electrode
We fabricated MgO barrier magnetic tunnel junctions (MTJs) with a Co3Mn alloy bottom and FeCoB top electrodes. The (001)-oriented epitaxial films of the metastable bcc Co3Mn disordered alloys obtained showed saturation magnetization of approximately 1640 emu/cm3. The transmission electron microscopy showed that the MgO barrier was epitaxially grown on the Co3Mn electrode. Tunnel magnetoresistance of approximately 150% was observed at room temperature after the annealing of MTJs at 350◦C, indicating that bcc Co3Mn alloys have relatively high spin polarization