Giant cryogenic magnetocaloric effect in mineral of gaudefroyite: Direct and indirect measurements

Abstract

The magnetic and magnetocaloric properties of gaudefroyite minerals were studied. The magnetocaloric effect was investigated by direct and indirect methods in the temperature range 4.2–40 K and magnetic field up to 10 T. The magnetization was measured in a low magnetic field (200 Oe) with zero-field cooled and field cooling protocol and previous observation of typical spin glass behavior was confirmed. The giant magnetic entropy changes with anisotropic behavior and maximums |ΔSm|= 17 J kg−1 K−1 (H||c) at 18 K and |ΔSm|= 20 J kg−1 K−1 (H||ab) at 12 K at an applied magnetic field 10 T were observed. The direct measurements of the magnetocaloric effect demonstrated the maximum of adiabatic temperature changes of ΔTad = 11 K at a magnetic field change of 10 T (H||ab) at 11.5 K. Obtained values of magnetocaloric parameters for the mineral of gaudefroyite are comparable to promising materials for magnetic crycooling technologies (for example, hydrogen (LH2) liquefaction) and have an advantage for the absence of rare-earth elements in the gaudefroyite.