Manipulation of temperature dependence of coercivity in isotropic nanocrystalline permanent magnets

The manipulation of the temperature dependence of coercivity, H/sub cJ/(T), in Nd-Fe-B-Ti-C-M (M = Ca, Sr, Bi and Ga) nanocrystalline permanent magnets by modifying the intergranular exchange coupling coefficients, J/sub eff/, is obtained. Such H/sub cJ/ manipulation is seen in a micromagnetic model describing the ratio of exchange energy and magnetocrystalline energy for a grain magnetically coupled to surrounding grains. The dependence of the absolute value of the temperature coefficient, alpha;(H/sub cJ/), between 296 K and 373 K on cooling rate is observed in annealed ribbons.