LAUSR

Abstract We report on the magnetic properties of isostructural oxides R6AO12 (R = a rare-earth element, A = Mo or W) with high concentrations of rare-earth elements. We measured the magnetization and specific heat. Tm6MoO12 is a van Vleck paramagnet with a nonmagnetic singlet ground state (GS). Ho6WO12 exhibits an antiferromagnetic long-range order (AFM LRO) lower than T N = 2.1 K and its GS is a magnetic quasi-doublet. Dy6WO12 shows an AFM LRO lesser than T N = 2.7 K and its GS is a magnetic Kramers doublet. Er6MoO12 and Er6WO12 are Curie-Weiss paramagnets at temperatures above 2 K and both have a magnetic Kramers doublet GS. We evaluated the magnetic entropy change. The temperature of the maximum magnetic entropy change for a magnetic-field change of 5 T is high (15 K) in Tm6MoO12 in spite of an oxide containing only rare-earth ions as the magnetic ions.