TUNABLE MAGNETIC REGENERATOR ALLOYS WITH A GIANT MAGNETOCALORIC EFFECT FOR MAGNETIC REFRIGERATION FROM SIMILAR-TO-20 TO SIMILAR-TO-290 K

A giant magnetocaloric effect (Delta S-mag) has been discovered in the GD(5)(SixGe1-x)(4) pseudobinary alloys, where x less than or equal to 0.5. For the temperature range between similar to 50 and similar to 2 80 K it exceeds the reversible (with respect to alternating magnetic f ield) Delta S-mag for any known magnetic refrigerant material at the c orresponding Curie temperature by a factor of 2-10. The two most strik ing features of this alloy system are: (1) the first order phase trans formation, which brings about the large Delta S-mag in Gd-5(SixGe1-x)4 , is reversible with respect to alternating magnetic field, i.e., the giant magnetocaloric effect can be utilized in an active magnetic rege nerator magnetic refrigerator; and (2) the ordering temperature is tun able from similar to 30 to similar to 276 K by adjusting the Si:Ge rat io without losing the giant magnetic entropy change. (C) 1997 American Institute of Physics.