Domain Wall Motion in Double Nickel–Iron Films

Abstract

Middelhoek and Wild¹ have recently measured mobilities for domain wall motion in double nickel–iron alloy which are significantly greater than those reported earlier by Patton and Humphrey² for similar films. Both groups have published mobility data for single layer films which are in good agreement^3,4. In an attempt to clarify the situation concerning double films, mobility measurements have been made for two of Middelhoek and Wild's double films, each with two 400 Å nickel–iron layers (80 per cent nickel) separated by 100 Å of silica, using the technique reported previously^2,4. For these films, a wall mobility value of 1.2 (±0.3) × 10⁴ cm/sec-Oe was obtained. Middelhoek and Wild's mobility of 4.1 × 10⁴ cm/sec-Oe for double films (440 Å nickel–iron layers separated by 100 Å of silica) is significantly larger than the present determination. These differences are too large to be explained by the 40 Å difference in nickel–iron layer thickness or the scatter in the data. The differences in mobility determination for similar films from the same laboratory, as measured by different laboratories, can only be due to differences in the experimental technique.