Effect of grain alignment on magnetic structure in nanoscale material

Intergranular exchange interactions act to bind nanograins in nanoscale magnetic materials into larger interaction domains with a magnetic structure considerably larger than that of a single grain. To investigate the effect of differing relative grain orientation on the scale of the interaction domains in melt-quenched Nd₂Fe₁₄B, a two-dimensional micromagnetic model has been used. The model consists of 18 grains characterized by the intrinsic properties of Nd₂Fe₁₄B. Two cases are considered; one with a narrow distribution of easy axis orientations centered along the applied field direction and one with a nearly isotropic easy axis distribution. Computational results confirm that the scale of the magnetic structure for well-aligned material is very large, while for isotropic material only a few grains can be coupled Into an interaction domain before the intergranular misalignment is large enough to pin domain walls and impede reversal