Magnetic properties of amorphous Fe73.5Cu1Mo3Si12.5Al1B9 alloy

The FINEMET type Fe73.5Cu1Mo3Si12.5Al1B9 (numbers indicate at.%) alloy has been synthesized using single wheel melt spinning technique. The samples have been thermally annealed at about 40 K less than the crystallization temperature for various durations. The samples show increase in Curie temperature of the amorphous phase with annealing. To get a better insight into their magnetic behaviour we have done spin wave analysis on the as-spun and thermally annealed samples and extracted the spin wave stiffness constant and mean square range of exchange interaction. Low temperature thermomagnetic measurements from 10 to 300 K were performed with an applied field of 0.5 T. The data were fitted using the Bloch equation. The value of the C/B ratio and the mean square range of exchange interaction were found to be characteristic of amorphous ferromagnets. The variation of spin wave stiffness constant is correlated to the changes in Curie temperature and the nature of the exchange interaction existing in this alloy is determined.