Magnetic Coupling between Two Ni-Fe Layers Separated by SiO Intermediate Layer

Abstract

Composite ferromagnetic films consisting of two non-magnetostrictive Ni–Fe layers separated by a SiO layer were prepared, and the magnetic coupling energy between these two layers was determined from the measurement of the transverse susceptibility. The coupling energy proved to have a form of εc=-Acos 2φ, where 2φ was the angle between the magnetization vectors of the two layers. The coupling energy constant A was positive when the thickness of the intermediate layer t was small, decreased monotonically with increasing t, passed through zero, and finally approached a finite negative value. In the present paper it is shown that this behavior can be interpreted quantitatively by combining two mechanisms; the one coming from the topography as proposed by Néel, and the other caused by the magnetic charges appearing at the edges of the two magnetic layers.