Magnetic Properties of Single Crystals of Silicon Iron

The magnetization curves for the [100], [110] and [111] directions of single crytals of iron containing 3.85 percent silicon were obtained from single crystal specimens cut in the form of hollow parallelograms so that the sides of each specimen were parallel to the tetragonal, digonal or trigonal axes, respectively. This method avoids the errors due to demagnetizing fields, inherent in previous measurements on single crystals. In addition to the well-known anisotropy at magnetizations above half of saturation, the data show for the first time considerable anisotropy at low magnetizations. A maximum permeability of 1,380,000 by far the highest ever reported for silicon iron, was observed in the [100] specimen after careful annealing. The magnetic anisotropy constants $K_1$ and $K_2$ were obtained from the magnetization curves and from torque measurements on a disk cut parallel to a (110) plane.