Magnetocaloric effect in terbium dihydrides: Heat capacity measurements

Abstract

The magnetocaloric effect (MCE) in the magnetic terbium dihydride TbH 1.92, TbH 2.03 and TbH 2.09 samples has been evaluated from the heat capacity C p ( T ) measurements under-zero field and 9 T. The MCE phenomena in the vicinity of the magnetic phase transitions in terms of the magnetic-entropy change, Δ S M , and adiabatic temperature change, Δ T a d , are reported. The magnetic-entropy changes, − Δ S M = ( S H − S 0 ) exhibit complex temperature dependence. They have negative values below the magnetic transition temperature T max (the inverse magnetocaloric effect) and change sign at higher temperatures going to the normal magnetocaloric effect. The absolute | Δ S M | maximum values are 1.55 J/mol K (9.62 J/kg K) for TbH 1.92, 2.0 J/mol K (12.42 J/kg K) for TbH 2.03 and 1.50 J/mol K (9.31 J/kg K) for TbH 2.09 at temperatures equal to 13 K, 12.5 K and 11.5 K, respectively. The Tb–H system provides magnetic refrigerants which induce adiabatic cooling of about Δ T a d ≈ 2 K during the magnetization process with a field of 9 T in the temperature range of 10–15 K.