Š. Zajac

On crystal-field spectroscopy based on specific heat and thermal expansion measurements: application to the TmCu2 intermetallic compound

An experimental study based on specific heat, thermal expansion, magnetisation and neutron diffraction measurements on polycrystal and single crystal of the orthorhombic TmCu2 compound is presented. The results are satisfactorily interpreted within a model involving the crystal and molecular field acting on the Tm3+ ions. The energy spectrum of the ground-state multiple 3H6 of Tm3+ with the isolated split lowest quasi-doublet ( Delta 1=5+or-1 K, Delta 2=68+or-3 K) is proposed. The appropriate sets of crystal-field parameters Vlm are obtained and discussed.

On the temperature dependence of the sublattice magnetizations in TbCu2

Abstract Calculations based on molecular and crystal field models were used for the interpretation of the temperature dependence of the sublattice magnetizations found by neutron diffraction in the antiferromagnetic compound TbCu 2 . The observed dependence is explained as a result of comparable amounts of exchange and crystal field energy in this compound.

Magnetic phase transitions in TmCu2

Magnetisation, susceptibility, resistivity and specific-heat measurements on TmCu2 reveal magnetic transitions at 3.3K, 3.9K, 4.3K and 6.3K, which reflect a change of magnetic structure and Neel temperature. These transitions are strongly field dependent. The behaviour of TmCu2 is very similar to that of ErCu2 and therefore a complicated magnetic structure should be expected.

Crystal field in TmCu2 compound

Abstract The crystal field splitting in orthorhombic TmCu 2 compound has been determined by the analysis of the specific heat and thermal expansion measurements. The crystal field parameters of second-order are in agreement and the parameters of fourth- and sixth-order are significantly different from that calculated in the point-charge model.

Crystal field effects in TmCu2 compound

The splitting of the3H6 multiplet has been estimated for the Tm3+ ion in the crystal electric field of the orthorhombic TmCu2 compound. Using the energy levels and appropriate eigenfunctions the crystal field only susceptibility has been calculated along the principal orthorhombic axes at temperatures 10 to 300 K. The obtained results are compared with our measurements of specific heat and paramagnetic susceptibility on polycrystalline sample.

Selected formulas for the magnetic susceptibility of systems with 4f-ions

Basic formula for the magnetic susceptibility of systems with 4f-ions within the LS-coupling scheme is introduced. The high temperature behaviour of thermodynamic average values is considered and the result is used for a high temperature expansion of the magnetic susceptibility. The results in the whole temperature range are given for systems described by one-particle Hamiltonians and effective one-particle Hamiltonians are considered. Explicit formulas are given for the case of a crystal field Hamiltonian and Heisenberg interaction Hamiltonian including molecular field approximation.