SWITCHING IN SINGLE-DOMAIN NANOSTRUCTURES AT FINITE TEMPERATURES

We study the finite temperature magnetization reversal of single domain nanostructures (particles and wires) of different materials with Monte Carlo and analytic techniques. The temperature, angular, and shape dependences of the switching field are calculated. For large structure diameters, there are different reversal mechanisms at different orientations of the external field. For small structure diameters growth usually starts with the nucleation and a subsequent depinning of domain walls at the end(s) of the structure. The nucleation energy of the domain wall in a magnetic field approaches zero near the coherent rotation limit at small aspect ratios and at fields less than the coherent rotation limit at large aspect ratios. As the domain wall energy approaches zero the domain wall width can remain finite. For small diameters there is a significant temperature dependence in the coercive field. For structures whose easy crystalline anisotropy axis is not along the major axis, a variety of switching scenario is observed. (C) 1995 American Institute of Physics.