Effects of Residual Deposition Atmosphere and Substrate Temperature on the Magnetic Anisotropy of Permalloy Thin Films

Abstract

In an attempt to determine the role of trapped impurity atoms in the magnetic anisotropy observed in Permalloy thin films, a specific, oil‐free vacuum system was developed which allowed rapid, simultaneous deposition (1000 Å/min) of 82% Ni‐18% Fe onto two glass substrates (one usually at liquid‐helium temperature, the other at various temperatures above liquid helium) with a deposition pressure better than 2×10⁻⁹ Torr. In all cases the films deposited onto the heated substrates appeared anisotropic while those deposited onto the cold substrates appeared isotropic at liquid‐helium, intermediate, and room temperatures (when examined in ultrahigh vacuum with a hysteresis loop tracer). It was found that an anisotropy could be introduced into the isotropic films by low‐temperature annealing. The results of this investigation indicate that a sufficiently low substrate deposition temperature can inhibit the formation of magnetic anisotropy. It was not possible to eliminate the anisotropy in this experiment by reducing the residual atmosphere.