Magnetocaloric effect in Fe-Zr-B-M (M=Mn, Cr, and Co) amorphous systems

The magnetocaloric effect (MCE) of the amorphous Fe-Zr-B-M (M=Mn, Cr, and Co) ribbons has been investigated. The MCEs of the Fe90-xZr10Bx (x=5, 10, 15, and 20) ribbons are enhanced with small amounts of boron addition. Furthermore, the Curie temperature of the specimens can be decreased to be about room temperature with appropriate Mn and Cr substitutions, but the MCE performance of the specimens drops only slightly. It is also found that the magnetic entropy change of the Co-substitution series of Fe85-yZr10B5Coy ribbons almost remains constant although the Curie temperature is increased to be about 400 K for y=5. Therefore, for the application of MCE refrigeration at above room temperature, the Fe85-yZr10B5Coy ribbons are preferred due to the constant MCE and the high refrigeration capacity of about 90 J/kg at the magnetic field change of 10 kOe. Moreover, the field dependence of the magnetic entropy change exhibits power dependence for all the studied specimens. In the ferromagnetic range, the exponent is close to 1. In the paramagnetic regime, well above the Curie temperature, the exponent is 2, in agreement with the Curie-Weiss law. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3054369]