Magnetocaloric effect across the metamagnetic transition in Dy₅Si₂Ge₂ single crystal

A single crystal of rare earth intermetallic compound Dy₅Si₂Ge₂ (Orthorhombic, Space group Pnma) has been prepared by Czochralski method. Magnetization of Dy₅Si₂Ge₂ single crystal has been measured with magnetic field applied (i) along b axis and (ii) parallel to ac plane. Although a same Neél temperature (T_N) of ∼55 K is obtained when 50 Oe field is applied along b axis and in ac plane, the magnitude of magnetization is substantially different. This T_N value is close to the antiferromagnetic ordering temperature of polycrystalline Dy₅Si₂Ge₂ as well. The magnetization vs field data at 1.8 K shows an ultra-sharp metamagnetic transition when field is applied along both the directions, in a critical field of about 28 kOe. It is observed that b axis is easy direction of magnetization. Magnetocaloric effect of this Dy₅Si₂Ge₂ crystal has been estimated using magnetization vs field data obtained at various temperatures. A maximum magnetic entropy change (ΔS_m ^max) of ∼−15.6 J/kg/K has been observed at 22 K with field along b axis and ΔS_m ^max is ∼−11.2 J/kg/K at 54 K when field is parallel to ac plane, for a field change of 50 kOe. Occurrence of metamagnetic transition at temperatures below T_N gives rise to a second peak at ∼22 K in the temperature dependent isothermal magnetic entropy change that leads to the observed large magnetocaloric effect.