Magnetic phase transitions and large magnetic entropy change with a wide temperature span in HoZn

Abstract

CsCl-type HoZn undergoes two successive magnetic phase transitions: (i) paramagnetic to ferromagnetic (FM) at TC∼72K and (ii) a spin reorientation (SR) at TSR∼26K. Magnetization and modified Arrott plots indicate that HoZn undergoes a second-order magnetic phase transition around TC. The obtained critical exponents have some small deviations from the mean-field theory, indicating a short range or a local magnetic interaction which is properly related to the coexistence of FM and SR transitions at low temperature. Two successive magnetic transitions in HoZn induce one broad pronounced peak together with a shoulder in the temperature dependence of the magnetic entropy change −ΔSM(T) curves, resulting in a wide temperature range with a large relative cooling power (RCP). For a field change of 0–7T, the maximum value of −ΔSM is 15.2J/kgK around TC with a large RCP value of 1124J/kg. The large reversible magnetocaloric effect (MCE) and RC indicate that HoZn is a good candidate for active magnetic refrigeration.