On the Determination of Magnetocrystalline Anisotropy Constants from Torque Measurements

Publisher Website
Google Scholar
Abstract
According to simple theory, torque measurements on cubic single‐crystal disks should give values for the crystal anisotropy constants, K1 and K2, that are independent of field above some minimum saturating field. Our experiments on {100} and {110} disks of 3¼% silicon‐iron, and previous experiments of others, show that this theory is inadequate. In a more refined theory it is assumed that the edges of the disk are not saturated even in high fields. The observed increase in the peak values of the torque with increasing field can be attributed to a very small variation of the net magnetization I as the disk is rotated in the field. This variation must be such that I is largest in the hard directions of magnetization and smallest in the easy directions. Direct observation of the domain patterns on a {100} disk appears to confirm these assumptions. For both {100} and {110} disks, K1′ (the effective value of K1) varies as 1−c/√H over the range 1000 to 20 000 oersteds. The corresponding K2′ values for the {110} disk show a more complicated dependence on H. Values of K1′ found from torque peaks differ somewhat from those obtained from torque slopes; the difference between the smaller K2′ values is much more serious. The discrepancy is attributed to the particular way in which I varies with disk rotation.

This publication has 6 references indexed in Scilit: