Two‐Level Singlet Magnetism in TbAsO₄ and TbVO₄

Abstract

Spect,roscopic and specific heat measurements are reported on two singlet magnets, TbAsO, and TbVO,. The ratios between the antiferromagnetic ordering temperature T N and the splitting A between the two singlets are TN/A = 1.58 and TN/A = 0.45, respectively. The experimentsshow considerable deviationsfroma molecular field theory but remarkably better agree with a self-consistent RPA calculation in which the experimentally determined exchange and dipole fields are used.Es wird iiber spektrdskopische Messungen und uber Messungen der spezifischen Warme an den beiden Singulett-Magnetika TbAsO, und TbVO, berichtet. Das Verhaltnis der antiferromagnetischen Ordnungstemperatur TN zum Abstand A zwischen den beiden Singuletts betragt T,/A = 1,58 fur TbAsO, und T,/A = 0,45 fur TbVO,. Die Experimente zeigen betrachtliche Abweichungen von der Molekularfeldtheorie; die Ubereinstimmung mit einer selbstkonsistenten RPA-Rechnung, in welcher die experimentell bestimmten Austauschund Dipolfelder eingesetzt werden, ist wesentlich besser.

Quadrupole ordering destruction and crossover in the Jahn–Teller compound TbVO4

“…[8]. The lower part of the ground multiplet of Tb 3+ ion in the tetragonal TbVO 4 in accordance with optical absorption spectroscopy [9,10] and Raman scattering studies [8,11] has a singlet-doublet-singlet pattern with a next doublet placed at $90 cm À1 . The CF from Ref.…”

“…The existence of this singlet was recognized by neither of the two procedures for any polarization. We have tried to clear away this contradiction by finding the CF on the basis of improved values of the ground multiplet splitting [10] with a constraint of no singlet below this doublet. All obtained sets of CF parameters have a sign of B 4 6 not characteristic for the vanadate series.…”

Zircon to scheelite phase transition induced by pressure and magnetism inTbCrO4

“…First, the lack of long-range magnetic ordering down to 61 mK reported for the isomorphous TbVO 4 -zircon compound ͑V 5+ , d 0 ͒ reveals the important role that the Cr 5+ plays as promoter of the magnetic interactions on the Tb 3+ sublattice. 35 Second, the superexchange Cr-O-O-Cr is hindered because of the poor orbital overlapping of chromium atoms located at the center of the isolated ͓CrO 4 ͔ tetrahedra that constitute zircon-and scheelite-type structures, see Fig. 2.…”

Effect of Gd polarization on the large magnetocaloric effect ofGdCrO4in a broad temperature range

“…Third, the exchange interaction between 3d ions, usually much higher than the R-R exchange interaction, provides an internal field, increasing the polarization of the R ions below the ferromagnetic ordering temperature. The Cr 5+ ion plays an important role as the promoter of the interactions in the rare-earth sublattice, increasing its ordering temperatures at least one order of magnitude in comparison with the analogous RXO 4 (X = P, As, V), where X is a diamagnetic element [24,25]. The case R = Gd is easier to analyze because, for this spin-only atom, the anisotropy and crystal-field energies are of the order of 1 K or less [24], therefore, a higher MCE is expected.…”