New Anisotropy Recorder for Ferromagnetic Thin Films

Abstract

A new instrument is presented for measurement of the anisotropy energy of thin ferromagnetic films. It permits rapid and simple investigation of the anisotropy over a 360° range. The method is purely electrical; the results are automatically displayed on the oscilloscope screen. The circular film is rotated uniformly in a homogeneous dc field. The magnetization vector oscillates around the direction of this field. Its movement is recorded, and relates directly to the anisotropy energy function. Three examples of results obtained are presented. The resolving power, expressed in terms of magnetic flux inside the sample, is determined by the ambient 60‐cycle field; its value is of the order of 10⁻¹¹ Wb, which corresponds to a thickness of approximately 10 Å for a 80% Ni Permalloy film one cm in diameter. The simplicity and the small cost of the instrument are attractive features. In many cases, both the present analysis and that obtained with a static torquemeter at high field would be complementary.