The role of grain boundaries in nanoscaled high-performance permanent magnets

Modern high-performance permanent magnets are based on rare-earth transition-metal intermetallic compounds like Nd2Fe14B. But the desired magnetic properties depend also on details of the grain structure, especially the magnetic properties of the grain boundaries. This paper reveals the effect of nonideal grain boundaries on the demagnetization process of realistic three-dimensional grain structures by using computational micromagnetism. In the presence of intergranular layers of about 3 nm thickness, the remanence and coercivity decreases approximately linearly for a simultaneous reduction of the intergranular exchange and anisotropy constant from 150% to 10% of their initial values. If these material parameters are reduced to values smaller than 10% of their initial values, the remanence and coercivity decreases strongly. (C) 1998 Elsevier Science B.V. All rights reserved.