Lorentz microscopy observation of magnetic domain structure variation in NiFe/Au multilayer films caused by Au layer thickness

摘要

Lorentz electron microscopy offers a very useful technique by which the magnetic domain structure of a thin film can be observed. In order to develop GMR materials with high sensitivity, it is desirable to understand the magnetic domain structure of the material. In this study, the magnetic domain structure of a series of NiFe/Au multilayer films (MLFs) with Au layer thickness between 1 nm and 4 nm has been observed using Lorentz microscopy. The MLFs showed a complicated domain structure, which contained twin walls and cross-tie walls in the MLFs. As the Au layer thickness increased so the ferromagnetic coupling between the NiFe layers decreased resulting in a more complex domain structure. In-situ magnetizing experiments showed that magnetic domain wall motion was the dominant mechanism for reversing the direction of magnetization. It is believed that reversal of the magnetization in the MLFs with thick Au layers was greatly affected by the structural defects in the films.