SIMPLE FUNCTION FOR A COMPLEX-DOMAIN CONFIGURATION

A complex domain configuration found in an iron whisker can be generat ed by a function with three parameters. The configuration is generated by passing a current along the axis of a (100) whisker with a square cross section. It has four domains in which the magnetization circulat es about a central domain magnetized along the z axis. There are four (110) 90 degrees walls and four (100) 90 degrees walls separating thes e domains. Two of the parameters are known a priori from micromagnetic s: a(1) describes type I 90 degrees walls between two domains with in- plane magnetization; and a(2) describes type II 90 degrees walls betwe en the domains with in-plane magnetization and the central domain with the magnetization out of the plane. The third parameter h, which dete rmines the width of the central domain, is adjustable to minimize the total micromagnetic energy in response to magnetic fields. The magneti zation pattern is generated from a vector potential A(x,y)(z) over til de. Calculating M(s) curl A(x,y)(z) over tilde produces M(x) and M(y). Then M(z) is found from M(x)(2)+M(y)(2)+M(z)(2)+M(s)(2). The potentia l has four parts: A(x,y)=A(x)+A(z)+A(h)+A(c), where A(x) and A(y) are the same function (with x and y interchanged) used to create the in-pl ane domains and the type I walls, A(h) generates the type II walls, an d A(c) describes the outer corners. The resulting magnetization is div ergence free. The analytic functions are convenient for calculation of the magnetic response to applied fields. (C) 1996 American Institute of Physics.