Exchange spring magnetic properties of Fe71(NdPr)4Co5Cu0.5Nb1B18.5 alloy

A melt-spun Fe71(NdPr)4Co5Cu0.5Nb1B18.5 amorphous alloy has been studied for their exchange spring behavior in the nanocrystalline state and hence its potential use as an exchange spring magnet. Steep recoil curves of the samples annealed at 870 and 970 K show the typical spring exchange characteristic with smaller loop area. Temperature dependence of (BH)max and the remanence ratio Mr/Ms have been investigated over a wide range of temperature from 5 up to 380 K using a superconducting quantum interference device (SQUID). It is observed that the temperature dependence of these parameters decrease with increasing temperature indicating gradual weakening of exchange coupling energy between the magnetic nanograins with the rise of temperature. A change in the shape of the hysteresis loop is observed below 100 K indicating a possible spin reorientation in the hard magnetic phase.