COMPUTED TEMPERATURE STABILITY OF THE REMANENCE AND THE COERCIVITY OFNANOSCALED PERMANENT-MAGNETS

For technical applications of high performance permanent magnets the s tability of magnetic properties like the remanence and the coercivity over a large temperature range is a decisive prerequisite. This can be investigated by computational methods using the continuum theory of m icromagnetism. For permanent magnets based on rare-earth transition-me tal intermetallic compounds and nanoscaled grain structures with isotr opically distributed easy axes, the temperature dependence of the rema nence is described by J(r)(T) = beta J(sat)(T)/2, where J(sat) is the saturation polarization of the magnetic material and beta a microstruc tural parameter. The temperature dependence of the coercivity call be described by H-c(T) = alpha H-N(min)(T) - N-eff J(s)(T)/mu(0), where K -N(min) = (K-1 + K-2)/J(s) is the minimum nucleation field, K-1 and K- 2 the anisotropy constants and J(s) the spontaneous polarization of ti e magnetic material. The numerical investigations allow to relate the microstructural parameters alpha, beta and N-eff to microstructural de tails and intergranular interactions like the short-range exchange int eraction and the long-range strayfields.