COMPOSITION DEPENDENCE OF MAGNETIC-PROPERTIES IN AMORPHOUS RARE-EARTH-METAL-BASED ALLOYS

Magnetic refrigeration is an emerging new technology for cooling and g as liquefaction. The proper selection of magnetic working materials pl ays a key role in any design of a magnetic refrigerator. Properly fabr icated amorphous rare-earth-metal-based alloys may be promising candid ates for magnetic refrigeration applications. Their advantages include tailorable composition, low eddy current and hysteresis losses, impro ved corrosion resistance, and large specific area. To optimize the com position, bulk magnetic properties of selected Re70M30-xTx (with Re = Gd, Dy, Er, Ho, Tb and M, T = Ni, Fe, Cu, Al) alloys have been investi gated in the 5-350 K temperature and 0-7 T DC field range. Far above t he magnetic transition, all investigated alloys display a Curie-Weiss behavior consistent with the effective atomic moment of the Re-atoms p resent. The composition dependence of the Weiss constant reveals that although influenced by the presence of transition metals, the Re-Re ex change plays the main role in magnetic interactions. Gd-based alloys d isplay a tendency to form multiple phases, which is supported by the p resence of Fe and suppressed by the addition of Al. Single-phase amorp hous Re70M30-xTx alloys are characterized by transition temperatures b elow 200 K, and in spite of their inherently broad transitions, they o ften display a magnetic entropy change superior or comparable to that of crystalline alloys with similar transition temperatures. Consequent ly, rare-earth-based amorphous alloys are promising candidates for mag netic refrigeration applications.