On crystal-field spectroscopy based on specific heat and thermal expansion measurements: application to the TmCu₂intermetallic compound

Abstract

An experimental study based on specific heat, thermal expansion, magnetisation and neutron diffraction measurements on polycrystal and single crystal of the orthorhombic TmCu, 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 multiplet 3H6 of Tm3+ with the isolated split lowest quasi-doublet (A, = 5 k 1 K, A2 = 68 -t 3 K) is proposed. The appropriate sets of crystal-field parameters V y are obtained and discussed.

Magnetoelastic interactions in the orthorhombic RECu2compounds (RE identical to Tb, Dy, Ho, Er, Tm)

“…The magnetoelastic effects have been reported earlier for a few R E C U ~ compounds [5,6] even in the paramagnetic temperature range. The main reason for this work is to extend the usual concept of the magnetoelastic Hamiltonian written in terms of the tensor operators and elastic strains to the case of the RECu2 compounds with orthorhombic symmetry and to discuss the connection with the experimental data now available.…”

“…(RE = rare earth) intermetallic compounds in the last decade [l-61. The results of inelastic neutron scattering [2], neutron diffraction [3], magnetisation [4], susceptibility [5] and specific heat measurements [6] revealed a significant crystal-field (CF) splitting of the localised 4f states of the RE^+ ion.…”

“…Let us consider that the term XME gives only a small perturbation of the CF energy levels ( A E , / E , = low4) in the RECU, compounds in the paramagnetic temperature range. Also the values of the Debye temperatures within the RECU2 series (0, = 200 K [5,6]) suggest that the elastic strains are small. Then in (2) we can limit ourselves to the secondorder terms in the total angular momentum operators J,, ly, J , and the elastic energy can be written as [lo]…”

Specific heat of geometrically frustrated and multiferroicRMn1−xGaxO3Zhou1, Janik2, Vogt3 et al. 2006Phys. Rev. B

“…͑1͒; ⌬ i is the ith energy level of crystal field in Kelvin. 19,20 Recent neutron scattering data 3 indicates two crystal field levels of Ho at 1.5 meV ͑17.4 K͒ and 3.1 meV ͑36 K͒, so here we chose i = 2. The solid curves shown in Fig.…”

Relief of frustration through spin disorder in multiferroicHo1−xYxMnO3

“…Here, ␤ = N͑12/ 5͒ 4 R D 3 with N = 5 as the number of atoms in the unit cell and R = 8.314 J / mol K as the ideal gas constant; A is a constant which specifies the percentage of the number of Ho 3+ ions per formula unit involved with the Schottky anomaly; x is the Y-doping percentage; and ⌬ i is the ith energy level of the crystal field in Kelvin. 19,20 For our temperature range, we choose i = 2 based upon the recent neutron scattering data, 21 which indicates there are two crystal field levels of Ho at 1.5 meV ͑17.4 K͒ and 3.1 meV ͑36 K͒. The solid curves shown in Fig.…”