Magnetic and some thermal properties of chalcogenides of Pr and Tm and a few other rare earths

Abstract

The magnetic properties of all known sulfides, selenides, and tellurides of Pr and Tm (as representative of the light and heavy rare earths, respectively) have been studied. In most cases, Pr and Tm compounds exhibit Van Vleck paramgnetism at low temperatures owing to crystal-field singlet ground states. Splittings have been derived in several cases by specific-heat measurements. In the case of Pr, X4 (X = S, Se,Te) compounds, specific-heat and susceptibility measurements reveal exchange-induced ferromagnetism. This is further supported by the study of the magnetic phase diagrams of Pr, Se4-Pr, Se3, La3Se4-Pr3Se4, and of superconductivity in the (La, "Pr"), (S4, Se4, Te4) series.Superconductivity persists to very high Pr concentrations, as in the Lal "Pr"Sesystem, indicating a nonmagnetic ground state of Pr. The higher chalcogenides appear to exhibit in general semimetallic or semiconducting behavior, while most of the metallic La compounds are usually superconductors.

Effect of chemical pressure on the charge density wave transition in rare-earth tritelluridesRTe3

“…15,16,17,18 There is a small but finite electronic contribution to the heat capacity, and the resistivity is observed to be metallic down to the lowest temperatures, confirming the presence of a small fraction of ungapped, reconstructed FS in the CDW state. 7,19,20 ARPES measurements have shown that the maximum value of the CDW gap scales with the lattice parameter, with published values of ∼280 meV for SmTe 3 15 and ∼400 meV for CeTe 3 . 16 This trend has been confirmed by optical conductivity measurements, which also reveal that the remaining fraction of ungapped FS in the CDW state is larger for compounds with smaller lattice parameters.…”

“…In this regard, rare-earth containing compounds are particularly valuable because the lattice parameter can be varied over a wide range in an almost continuous fashion while keeping the band filling essentially unchanged. The rare earth tritelluride RTe 3 compounds form for almost the entire rare-earth series, with R = La-Nd, Sm, Gd-Tm, 3,4,5 and provide a unique opportunity to follow the effect of chemical pressure on FS nesting and CDW formation.…”

Spin dynamics and magnetic ordering in mixed valence systems

“…order iri TmSe has not been clear. Early neutron diffraction experiments in a polycrystalline sample were amb.iguous [6], but more recent macroscopic measurements suggest.ed a well-defined phase transition at T rv 3 K [7][8][9][10][11]. The situation in TmSe is eve.n more complex because results appear to be very sample dependent [11,12].…”

Ultrasonic wave propagation in rare-earth monochalcogenides

“…The temperature dependent resistivity, thermo e.m.f., thermal conductivity, and ultrasonic pa-rameters are presented for ReX(Re=La, Ce, Pr, Nd, Sm, Eu, Tm; X=S, Se and Te) by various investigators [7][8][9][10][11][12][13][14][15]. Bucher et al studied the magnetic and thermal properties of all known sulfides, selenides and tellurides of praseodymium and thulium [16]. Batlogg interpreted valence of the Tm ions in mixed valent TmSe by alloying with TmTe and EuSe in order to study intermediate-valent rare-earth ions as a function of the degree of valence mixing [17].…”

“…Tm compounds exhibit Van Vleck paramgnetism at low temperatures as a consequence of the crystal-field singlet ground states [16]. TmS, TmSe and TmTe are golden metal, red brown colored intermediate valance system, and silver blue semiconductor, respectively [1].…”