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

Lorentz electron microscopy offers a very useful technique by which the mag netic domain structure of a thin film can be observed. In order to develop GMR materials with high sensitivity, it is desirable to understand the magn etic domain structure of the material. In this study, the magnetic domain s tructure of a series of NiFe/Au multilayer films (MLFs) with Au layer thick ness 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 fer romagnetic coupling between the NiFe layers decreased resulting in a more c omplex domain structure. In-situ magnetizing experiments showed that magnet ic domain wall motion was the dominant mechanism for reversing the directio n of magnetization. It is believed that reversal of the magnetization in th e MLFs with thick Au layers was greatly affected by the structural defects in the films.