Magnetic properties of Dy-Zr nanocomposites

As part of a search for materials which exhibit enhanced magnetocaloric eff ect, the magnetic properties of amorphous Dy70Zr30 and DY30Zr70 alloys were investigated in the temperature range of 5-300 K and at magnetic fields up to 7 T. The results show that these materials can be described as nanocomp osites, with interacting clusters below a critical temperature T-F and simp le paramagnetism above 120 K. Below 120 K the magnetization is history depe ndent up to a critical field determined by the composition. Field cooling r esults in a shift of the low-temperature hysteresis loop along the magnetiz ation axis, without influencing the shape. The magnetic entropy change peak s at the same temperature for both compositions, with a composition-depende nt peak height, offering a unique tunability of the magnetocaloric effect. The results are interpreted in terms of existing theories of cluster glasse s. [S0163-1829(99)06601-1].