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.