22 research outputs found
Quadrupolar interactions in heavy fermion metal YbRh2Si2
We describe the experimentally revealed by Sichelschmidt et al, Phys. Rev.
Lett. 91 (2003) 156401, g tensor, g_perpendicular=3.561 and g_parallel=0.17, at
5 K by means of crystal field interactions of the 4f13 configuration of the
Yb3+ ion of YbRh2Si2 in a slightly orthorhombically distorted tetragonal
crystal field. We have shown that the temperature dependence of the quadrupolar
interactions Q(T) of the Yb nucleous will help to distinguish between Gamma_7
and Gamma_6 ground state. For the Gamma_7 ground state Q(T) is expected to
exhibits an anomalous dependence.
Keywords: heavy fermion, crystal field, quadrupolar moment,YbRh2Si2Comment: 2 pages LaTeX(Elsevier Science class), 1 figur
Ground state, electronic structure and magnetism of LaMnO3
We have calculated the discrete low-energy electronic structure in LaMnO3
originating from the atomic-like states of the strongly correlated 3d4
electronic system occurring in the Mn3+ ion. We take into account very strong
intra-atomic correlations, crystal field interactions and the intra-atomic
spin-orbit coupling. We calculated magnetic and paramagnetic state of LaMnO3
within the consistent description given by Quantum Atomistic Solid State Theory
(QUASST). Our studies indicate that the intra-atomic spin-orbit coupling and
the orbital magnetism are indispensable for the physically adequate description
of electronic and magnetic properties of LaMnO3.
Keywords: 3d oxides, crystal field, spin-orbit coupling, LaMnO3
PACS: 71.70Ej, 75.10DgComment: 5 pages, 2 figures, in RevTex
Orbital moment in CoO and in NiO
The total, orbital and spin moment of the Co2+ ion in CoO has been calculated
within the quasi-atomic approach with taking into account strong correlations,
crystal-field interactions and the intra-atomic spin-orbit coupling. The
orbital moment of 1.39 \mu B amounts at 0 K, in the magnetically-ordered state,
to more than 34% of the total moment (4.01 \mu B). The same calculations yield
for NiO the orbital and total moment of 0.46 \mu B and 2.45 \mu B,
respectively.
PACS No: 71.70.E; 75.10.D
Keywords: 3d magnetism, crystal field, spin-orbit coupling, orbital moment,
CoO, NiOComment: 6 pages in tex+3 figs, submitted for PNSXM-03, Venic
Strongly correlated crystal-field approach to Mott insulator LaCoO3
Our success in description of recent electron-spin-resonance results on Mott
insulator LaCoO3, Phys. Rev. B 67 (2003) 172401, lies in taking into account
strong electron correlations among d electrons and the relativistic spin-orbit
coupling. In the developed by us Quantum Atomistic Solid State Theory (QUASST)
we assume that the atomic-like integrity of the 3d^6 system is preserved in the
Co^3+ ion in LaCoO3 and that intra-atomic correlations are much stronger than
crystal field interactions. We conclude that in LaCoO3 there is no intermediate
spin state as came out from band-structure calculations. The excited states
originate from the high-spin 5T2g term, being 12 meV above the ground 1A1
state. We are convinced that many-electron CEF approach with strong
correlations and the atomic-scale orbital magnetism is physically adequate
approach to 3d oxides.
Keywords: Mott insulator, crystal field, spin-orbit coupling, LaCoO3Comment: 5 pages, 3 figures in RevTeX
Electronic and Magnetic Properties of Febr2
Electronic and magnetic (e-m) properties of FeBr2 have been surprisingly well
described as originating from the Fe2+ ions and their fine electronic
structure. The fine electronic structure have been evaluated taking into
account the spin-orbit (s-o) coupling, crystal-field and inter-site
spin-dependent interactions. The required magnetic doublet ground state with an
excited singlet at D=2.8 meV results from the trigonal distortion. This effect
of the trigonal distortion and a large magnetic moment of iron, of 4.4 mB, can
be theoretically derived provided the s-o coupling is correctly taking into
account. The obtained good agreement with experimental data indicates on
extremaly strong correlations of the six 3d electrons in the Fe2+ ion yielding
their full localization and the insulating state. These calculations show that
for the meaningful analysis of e-m properties of FeBr2 the spin-orbit coupling
is essentially important and that the orbital moment (0.74 mB) is largely
unquenched (by the off-cubic trigonal distortion in the presence of the
spin-orbit coupling).Comment: 11 pages in RevTex, 5 figure
Calculation of magnetic anisotropy energy in SmCo5
SmCo5 is an important hard magnetic material, due to its large magnetic
anisotropy energy (MAE). We have studied the magnetic properties of SmCo5 using
density functional theory (DFT) calculations where the Sm f-bands, which are
difficult to include in DFT calculations, have been treated within the LDA+U
formalism. The large MAE comes mostly from the Sm f-shell anisotropy, stemming
from an interplay between the crystal field and the spin-orbit coupling. We
found that both are of similar strengths, unlike some other Sm compounds,
leading to a partial quenching of the orbital moment (f-states cannot be
described as either pure lattice harmonics or pure complex harmonics), an
optimal situation for enhanced MAE. A smaller portion of the MAE can be
associated with the Co-d band anisotropy, related to the peak in the density of
states at the Fermi energy. Our result for the MAE of SmCo5, 21.6 meV/f.u.,
agrees reasonably with the experimental value of 13-16 meV/f.u., and the
calculated magnetic moment (including the orbital component) of 9.4 mu_B agrees
with the experimental value of 8.9 mu_B.Comment: Submitted to Phys. Rev.