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R. J. Radwanski Z. Ropka

Publications and source records attributed to R. J. Radwanski Z. Ropka.

5 recordsLinked to original sources
arXiv2008

Electronic structure and magnetism of a ferromagnetic insulator Cs2AgF4: explanation for a lilac colour and a prediction for the anisotropic g factor

Magnetic properties of stechiometric Cs2AgF4 have been calculated within a very strong correlation limit taking into account a low-symmetry crystal field and the intra-atomic spin-orbit coupling of the Ag2+ ion. We consistently explain the insulating ground state and the magnetic state revealing the spin gap of 2.6 meV below Tc of 14.9 K. A d-d excitation of 2.0-2.3 eV related to the t2g-eg promotion energy (=10Dq) is a reason for the lilac colour of Cs2AgF4. Our approach can be experimentally verified by the measurement of the g factor (gz =2.12 and gy =2.52) and the absorption energy at 2.0-2.3 eV.

cond-mat.str-el↗
arXiv2006

Crystal-field states in NaCoO2 and in wet cobalt superconductors (NaxCoO2)

We claim that for calculations of the electronic structure of 3d oxides very strong electron correlations have to be taken into account similarly to those assumed in many-electron crystal field approach. For Co3+ ions in NaxCoO2.yH2O there are 15 low lying many-electron states within 0.1 eV as can be obtained in the many-electron CEF approach with taking into account the spin-orbit coupling. We claim, that the used by us Hamiltonian for the trigonal distortion is correct.

cond-mat.str-el↗
arXiv2005

Crystal field states in conducting magnetic materials: NdAl2, UPd2Al3 and YbRh2Si2

The existence of CEF states and the magnetism in conducting compounds NdAl2, UPd2Al3 and YbRh2Si2 is discussed. We point out that in metallic compounds localized crystal-field states coexist with conduction electrons. These compounds are physical realization of an anisotropic spin liquid, which in case of the atomic-like configuration with an odd number of f electrons, is unstable with respect to spin fluctuations for T->0K. YbRh2Si2 is discussed as a compound with the Kramers doublet ground state with a very low magnetic ordering temperature being a reason for the quantum critical point phenomena at low T.

cond-mat.str-el↗
arXiv2005

Electronic structure and magnetism of LaVO3 and LaMnO3

In this contribution we derive and discuss energy levels of the strongly-correlated d2 configuration of the V3+ ion (LaVO3) and of d4 configuration of the Mn3+ ion (LaMnO3) in the octahedral surroundings in the presence of the spin-orbit coupling and the resulting magnetic properties. We take into account very strong correlations among the d electrons and work with strongly-correlated atomic-like electronic systems, ground term of which is, also in a solid, described by two Hund's rules quantum numbers. In a solid we take into account the influence of crystal-field interactions, predominantly of the cubic (octahedral) symmetry. We describe both paramagnetic state and the magnetically-ordered state getting a value of 1.3 uB for the V3+ -ion magnetic moment in the ordered state at 0 K for LaVO3 (3T1g) and of 3.7 uB for LaMnO3 (5Eg). A remarkably consistent description of both zero-temperature properties and thermodynamic properties indicates on the high physical adequacy of the applied atomic approach. We point out the necessity to unquench the orbital moment in 3d-ion compounds. We claim that the intra-atomic spin-orbit coupling and strong electron correlations are indispensable for the physically adequate description of electronic and magnetic properties of LaVO3 and LaMnO3.

cond-mat.str-el↗