335 research outputs found
Spin-polarized scanning tunneling microscopy of half-metallic ferromagnets: Non-quasiparticle contributions
The role of the many-body (spin-polaronic) effects in the scanning tunneling
spectroscopy of half-metallic ferromagnets (HMF) is considered. It is shown
that the non-quasiparticle (NQP) states exist in the majority or minority spin
gap in the presence of arbitrary external potential and, in particular, at the
surfaces and interfaces. Energy dependence of the NQP density of states is
obtained in various models of HMF, an important role of the hybridization
nature of the energy gap being demonstrated. The corresponding temperature
dependence of spin polarization is calculated. It is shown that the NQP states
result in a sharp bias dependence of the tunneling conductance near zero bias.
Asymmetry of the NQP states with respect to the Fermi energy provides an
opportunity to separate phonon and magnon peaks in the inelastic spectroscopy
by STM.Comment: 13 pages, 6 figure
Pseudofermion ferromagnetism in the Kondo lattices: a mean-field approach
Ground state ferromagnetism of the Kondo lattices is investigated within
slave fermion approach by Coleman and Andrei within a mean-field approximation
in the effective hybridization model. Conditions for formation of both
saturated (half-metallic) and non-saturated magnetic state are obtained for
various lattices. A description in terms of universal functions which depend
only on bare electron density of states (DOS) is presented. A crucial role of
the energy dependence of the bare DOS (especially, of DOS peaks) for the
small-moment ferromagnetism formation is demonstrated.Comment: Final version, Eur. Phys. J. B, accepte
Sum rules for X-ray magnetic circular dichroism spectra in strongly correlated ferromagnets
It is proven that the sum rules for X-ray magnetic dichroism (XMCD) spectra
that are used to separate spin and orbital contributions to the magnetic moment
are formally correct for an arbitrary strength of electron-electron
interactions. However, their practical application for strongly correlated
systems can become complicated due to the spectral density weight spreading
over a broad energy interval. Relevance of incoherent spectral density for the
XMCD sum rules is illustrated by a simple model of a ferromagnet with orbital
degrees of freedom.Comment: 4 pages, final versio
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