arXiv subjects

Z. Ropka

Publications and source records attributed to Z. Ropka.

60 records · Page 4Linked to original sources

arXiv2000

Crystal-field interactions in PrRu2Si2

Ferromagnetic compound PrRu2Si2 exhibits a giant magnetocrystalline anisotropy of about 400 T. Its ordered moment below Tc=14K reaches 2.7 mB and is parallel to [0 0 1] crystalline direction. We have attributed the magnetism of PrRu2S2 to the Pr ions and performed calculations of the fine electronic structure of the Pr ion in the tetragonal symmetry, relevant to PrRu2Si2 taking into account crystal-field and inter-site, spin-dependent exchange interactions. Spin-dependent interactions have been taken into account by means of molecular-field approximation. The derived energy level scheme is associated with the removal of the degeneracy of the lowest multiplet given by Hund's rules, 3H4. Magnetic and electronic properties resulting from this fine structure are compared with all known experimental results. Our calculations reproduce well the zero-temperature moment, temperature dependence of the magnetic susceptibility, single-crystalline magnetization curves with the anisotropy field of 400T, the specific heat with the sharp peak at Tc as well as inelastic-neutron-scattering data.

cond-mat.str-el↗

arXiv2000

The orbital moment in NiO

The orbital and spin moment of the Ni2+ ion in NiO has been calculated within the quasi-atomic approach. The orbital moment of 0.54 mB amounts at 0 K, in the magnetically-ordered state, to more than 20% of the total moment (2.53 mB). For this outcome, being in nice agreement with the recent experimental finding taking into account the spin-orbit coupling is indispensable.

cond-mat.str-el↗

arXiv2000

Giant Sommerfeld coefficient in the heavy-fermion YbBiPt

It has been derived that the Sommerfeld coefficient $γ$ as large as 25 J/K$^2$mol can be theoretically accounted for provided the charge f-electron fluctuations are substantially suppressed. This result enables the understanding of the heavy-fermion YbBiPt ($γ$ =8 J/K$^2$mol) as the spin fluctuator and should stimulate the experimental specific-heat research at low temperatures.

cond-mat.str-el↗

arXiv1999

Relativistic effects in the electronic structure for the 3d paramagnetic ions

It has been shown that relativistic spin-orbit effects have enormous influence on the electronic structure of the correlated electron systems 3dn. The s-o coupling produces the fine electronic structure with a large number of low- energy, < 10 meV, localized states, These states affect enormously electronic and magnetic properties of 3d-ion compounds at low- and room-temperature regions. It is inferred that the relativistic s-o effects and the multiplet structure on individual atoms are indispensable for the proper evaluation of the electronic structure of paramagnetic 3d ions.

cond-mat.str-el↗

arXiv1999

Anomalous temperature dependences of the susceptibility for the one-3d- electron cation

We have studied properties of the one-3d-electron cation (Ti 3+, V 4+ ions) under the action of the low-symmetry crystal field in the presence of the spin- orbit coupling. Very anomalous temperature dependences of the magnetic susceptibility chi (T) have been obtained as resulting from the off-cubic lattice distortion provided the intra-atomic spin-orbit coupling is taken into account. It indicates that, despite of the weakness of the spin-orbit coupling, the one 3d electron in a solid cannot be treated as a free S=1/2 spin. The same holds for compounds containing the Ti 3+ and V4+ ions.

cond-mat.str-el↗

arXiv1999

The formation of a non-magnetic state for the d6 electronic system

It has been shown that the crystal-field interactions can produce a non- magnetic singlet ground state for the highly-correlated d6 system situated in the quasi-octahedral crystal field (CEF) surrounding provided the spin-orbit interactions are correctly taking into account. The spin-orbit interactions in combination with the trigonal distortion of the cubic CEF interactions produce a peculiar energy level scheme with a non-magnetic ground state and highly- magnetic excited states at 11 and 70 meV. The calculated temperature dependence of the magnetic susceptibility exhibits very substantial departure from the Curie law that is due to second-order CEF interactions. The present considerations can be applied to Co3+ and Fe2+- ion compounds. The derived electronic and magnetic properties mimic very much those found experimentally for LaCoO3.

cond-mat.str-el↗