Magnetic states and magnetization reversal in magnetostatically coupled multilayers with low perpendicular anisotropy

摘要

Multilayers of (F/NF)_N composition, where F means a ferromagnetic layer, NF a nonferromagnetic one, and N the number of repetitions, are studied by simulations and theoretically for different magnetic anisotropy characterized by the quality factor, Q (the ratio of the anisotropy energy to be gained by a magnetization along the easy axis perpendicular to the sample surface and the magnetostatic energy of a uniformly magnetized layer along the surface normal). It is shown that the range of the existence of out-of-plane magnetization states could be extended to Q < 1 by proper choice of N and the layers thicknesses. The role of magnetostatic interlayer coupling in the formation of vortexlike and sinusoidal-like distributions of the magnetization is revealed. Different magnetization states are mapped onto a (Q,N)-phase diagram. We demonstrate that a (F/NF)_N multilayer is a soft magnetic system in which the domain size could be changed by a few orders of magnitude by small variations of Q, N, and/or the NF spacer thickness. The evolution of magnetization distributions under applied in-plane and perpendicular magnetic fields is studied, as well as calculating the saturation fields and their dependences on Q and N.