Pinning effect of the grain boundaries on magnetic domain wall in FeCo-based magnetic alloys

We have studied the dynamics of grain growth and the pinning effect of grai n boundaries on magnetic domain walls in FeCo soft magnetic alloys. It has been found that grain growth takes place at temperatures above 600 degrees C. The activation energy for grain growth in a disordered state at 820 degr ees C is about 57.4+/-0.5 kcal/ mole. The effect of grain size on magnetic properties has been singled out by keeping the same ordering parameter (S = 0 and 0.88) for all samples studied. Microstructural characterization and magnetic measurements indicate that the grain size significantly affects th e magnetic coercivity. A linear relationship between the coercivity and the reciprocal of the grain size has been universally found regardless of the heat-treatment histories. Lorenz microscopic observation demonstrates that grain boundaries act as pinning sites for the magnetic domain wall movement . (C) 1999 American Institute of Physics. [S0021-8979(99)03309-5].