234 research outputs found
Reorientation phase transitions in thin magnetic films: a review of the classical vector spin model within the mean field approach
The ground state and the finite temperature phase diagrams with respect to
magnetic configurations are studied systematically for thin magnetic films in
terms of a classical Heisenberg model including magnetic dipole-dipole
interaction and uniaxial anisotropy. Simple relations are derived for the
occurrence of the various phase boundaries between the different regions of the
magnetic orientations. In particular, the range of the first and second order
reorientation phase transitions are determined for bi- and trilayers.Comment: 23 pages, LaTeX + 7 figures (Encapsulated PostScript), submitted to
Philosophical Magazine B (Feb. 28, 2001
Formation of magnetic skyrmions with tunable properties in PdFe bilayer deposited on Ir(111)
We perform an extensive study of the spin-configurations in a PdFe bilayer on
Ir(111) in terms of ab initio and spin-model calculations. We use the
spin-cluster expansion technique to obtain spin model parameters, and solve the
Landau-Lifshitz-Gilbert equations at zero temperature. In particular, we focus
on effects of layer relaxations and the evolution of the magnetic ground state
in external magnetic field. In the absence of magnetic field, we find a
spin-spiral ground state, while applying external magnetic field skyrmions are
generated in the system. Based on energy calculations of frozen spin
configurations with varying magnetic field we obtain excellent agreement for
the phase boundaries with available experiments. We find that the wave length
of spin-spirals and the diameter of skyrmions decrease with increasing inward
Fe layer relaxation which is correlated with the increasing ratio of the
nearest-neighbor Dzyaloshinskii-Moriya interaction and the isotropic exchange
coupling, . Our results also indicate that the applied field needed to
stabilize the skyrmion lattice increases when the diameter of individual
skyrmions decreases. Based on our observations, we suggest that the formation
of the skyrmion lattice can be tuned by small structural modification of the
thin film.Comment: 7 pages, 5 figures, 2 table
Exchange Bias driven by Dzyaloshinskii-Moriya interactions
The exchange bias effect in compensated IrMn3/Co(111) system is studied using
multiscale modeling from "ab initio" to atomistic calculations. We evaluate
numerically the out-of-plane hysteresis loops of the bi-layer for different
thickness of the ferromagnetic layer. The results show the existence of a
perpendicular exchange bias field and an enhancement of the coercivity of the
system. In order to elucidate the possible origin of the exchange bias, we
analyze the hysteresis loops of a selected bi-layer by tuning the different
contributions to the exchange interactions across the interface. Our results
indicate that the exchange bias is primarily induced by the
Dzyaloshinskii-Moriya interactions, while the coercivity is increased mainly
due to a spin-flop mechanism
Layer-resolved optical conductivity of Co|Pt multilayers
The complex optical conductivity tensor is calculated for the Co|Pt systems
by applying a contour integration technique within the framework of the
spin-polarized relativistic screened Korringa-Kohn-Rostoker method. It is shown
that the optical conductivity of the Co|Pt multilayer systems is dominated by
contributions arising from the Pt cap and/or substrate layers.Comment: 7 pages (LaTeX), 2 (a,b) figures (Encapsulated PostScript), J. Magn.
Magn. Materials, in pres
Atomistic spin-model based on a new spin-cluster expansion technique: Application to the IrMn3/Co interface
In order to derive tensorial exchange interactions and local magnetic
anisotropies in itinerant magnetic systems, an approach combining the
Spin-Cluster Expansion with the Relativistic Disordered Local Moment scheme is
introduced. The theoretical background and computational aspects of the method
are described in detail. The exchange interactions and site resolved anisotropy
contributions for the IrMn3/Co(111) interface, a prototype for an exchange bias
system, are calculated including a large number of magnetic sites from both the
antiferromagnet and ferromagnet. Our calculations reveal that the coupling
between the two subsystems is fairly limited to the vicinity of the interface.
The magnetic anisotropy of the interface system is discussed, including effects
of the Dzyaloshinskii-Moriya interactions that appear due to symmetry breaking
at the interface.Comment: 10 pages, 6 figure
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