The effect of cooling rate on magnetothermal properties of Fe49Rh51

Abstract

We have investigated the effects of quenching rate on the thermal dependence of the magnetic entropy change ΔSM(T) and the magnetic field induced hysteresis loss through the antiferromagnetic (AFM) ↔ ferromagnetic (FM) transformation in bulk Fe49Rh51. Two nearly identical square-prism-shaped samples were subjected to two different temperature cooling regimes; one was rapidly quenched (FQ) in iced-water and another slow cooled (SC) to room temperature at a cooling rate of 2 K/min. The temperature of the AFM↔FM transition is similar for both samples, but the FQ sample shows much sharper temperature- and magnetic field-induced magnetization change; in addition, the total magnetization change is 14 % larger. In FQ material, the magnetocaloric effect, i.e., ΔSM(T) quickly approaches saturation above 1 T and shows a large peak value at 2 T (13.9 versus 8.9 Jkg-1K-1 in SC material), but a larger average hysteresis loss <HL>FWHM in the temperature range coinciding with of the full-width at half-maximum of the ΔSM(T) curve.