Heat capacity and magnetocaloric effect in the zircon and scheelite phases of RCrO4, R 1/4 Tb, Er, Ho

We present here new magnetization and heat capacity data under magnetic field and direct measurements of the magnetocaloric effect (MCE) in the zircon and the new scheelite phases of RCrO4 (R = Tb, Er, Ho) from 5 K to 100 K, for magnetic fields B from 0 to 9 T. Zircons have a high MCE near their Curie point, TC similar or equal to 20 K, reaching maximum isothermal entropy increments, |Delta S-T| = 21, 19.4, and 16.2 J kg(-1) K-1 for HoCrO4, ErCrO4, and TbCrO4, respectively, for an external field of 5 T. TbCrO4 has another anomaly near T-D = 60 K associated to a Jahn-Teller transition from the tetragonal zircon structure to an orthorhombic phase. Scheelites are antiferromagnetic with TN similar or equal to 25 K. In the Tb scheelite the rare earth is strongly coupled to Cr5+ and the MCE exhibits the typical features of an antiferromagnet, i.e. a sort of Curie-Weiss behavior above TN and a sudden drop to small or even inverse values below. In the Er and Ho scheelites the R3+ -Cr5+ exchange coupling is very weak and the R3thorn ion behaves independently of the Cr5thorn. As a striking consequence the MCE is quite stronger well below TN.

Automated summary

In this study, magnetization and heat capacity measurements were conducted on new phases of zircon and scheelite materials to investigate their magnetocaloric effect (MCE) under different temperatures and magnetic fields. The results showed that zircons exhibit a high MCE near their Curie point, while scheelites demonstrate antiferromagnetic behavior. The behavior of rare earth elements also differs in scheelite materials.