46 research outputs found
Electronic structure and magnetic properties of epitaxial FeRh(001) ultra-thin films on W(100)
Epitaxial FeRh(100) films (CsCl structure, thick), prepared
{\it in-situ} on a W(100) single crystal substrate, have been investigated via
valence band and core level photoemission. The presence of the
temperature-induced, first-order, antiferromagnetic to ferromagnetic
(AF FM) transition in these films has been verified via linear
dichroism in photoemission from the Fe 3 levels. Core level spectra indicate
a large moment on the Fe atom, practically unchanged in the FM and AF phases.
Judging from the valence band spectra, the metamagnetic transition takes place
without substantial modification of the electronic structure. In the FM phase,
the spin-resolved spectra compare satisfactorily to the calculated
spin-polarized bulk band structure.Comment: 7 pages, 5 figure
Dynamics of the magnetic and structural a -> e phase transition in Iron
We have studied the high-pressure iron bcc to hcp phase transition by
simultaneous X-ray Magnetic Circular Dichroism (XMCD) and X-ray Absorption
Spectroscopy (XAS) with an X-ray dispersive spectrometer. The combination of
the two techniques allows us to obtain simultaneously information on both the
structure and the magnetic state of Iron under pressure. The magnetic and
structural transitions simultaneously observed are sharp. Both are of first
order in agreement with theoretical prediction. The pressure domain of the
transition observed (2.4 0.2 GPa) is narrower than that usually cited in
the literature (8 GPa). Our data indicate that the magnetic transition slightly
precedes the structural one, suggesting that the origin of the instability of
the bcc phase in iron with increasing pressure is to be attributed to the
effect of pressure on magnetism as predicted by spin-polarized full potential
total energy calculations
Lattice dynamics and structural stability of ordered Fe3Ni, Fe3Pd and Fe3Pt alloys
We investigate the binding surface along the Bain path and phonon dispersion
relations for the cubic phase of the ferromagnetic binary alloys Fe3X (X = Ni,
Pd, Pt) for L12 and DO22 ordered phases from first principles by means of
density functional theory. The phonon dispersion relations exhibit a softening
of the transverse acoustic mode at the M-point in the L12-phase in accordance
with experiments for ordered Fe3Pt. This instability can be associated with a
rotational movement of the Fe-atoms around the Ni-group element in the
neighboring layers and is accompanied by an extensive reconstruction of the
Fermi surface. In addition, we find an incomplete softening in [111] direction
which is strongest for Fe3 Ni. We conclude that besides the valence electron
density also the specific Fe-content and the masses of the alloying partners
should be considered as parameters for the design of Fe-based functional
magnetic materials.Comment: Revised version, accepted for publication in Physical Review
On the oxidation ofα-Fe andε-Fe2 N1−z II. Residual strains and blisters in the oxide layer
Moment-volume instabilities in Ti
We measured the thermal expansion and the specific heat of TixFe100-x alloys
with x = 30.5, 32.5 and 35,
all with hexagonal C14 laves phase structure (MgZn2)
like TiFe2, and determine the
temperature dependence of the magnetic
contributions to the thermal
expansion
and the specific heat cmag. For
fixed composition
and show the same type of behavior,
demonstrating that both anomalies are of
the same microscopic nature. They
originate from moment-volume fluctuations
(antiferromagnetic Invar-effect) as a
comparison with total energy calculations
as a function of atomic volume and
moment for TiFe2 reveals