Joule heating as a technique for obtaining uncoupled soft and hard magnetic phases in a Finemet alloy

A detailed study on the microstructural evolution of the Fe73.9Cu0.9Nb3.1Si13.2B8.9 (Finemet) alloy upon Joule heating and its correlation with the magnetic properties is reported. Mossbauer spectroscopy suggests the coexistence of soft nonstoichiometric Fe3Si and hard iron boride magnetic phases. The uncoupled magnetic character of these phases is evidenced by dc-hysteresis loop measurements. X-ray diffraction results display an excellent agreement with the magnetic characterization. The magnetic contribution of the soft phase has been decreased from 70% to 10% with increasing annealing current and time. The switching field value for the soft magnetic phase is 50 A/m, which is very less as compared to 2000 A/m, for the hard magnetic phase. Existence of uncoupled soft and hard magnetic phases makes these systems suitable for use as magnetic labels. (c) 2007 American Institute of Physics.