Magnetic properties of ordered Pt-Co

The alloy Pt-Co 50 atomic percent may be ordered into a tetragonal structure of the CuAu type. An ordered single crystal consists of a system of tetragonal crystallites, whose axes are oriented parallel to the three rectangular axes Ox, Oy, and Oz of the disordered matrix. Our study has been performed at room temperature on an ordered macrocrystal where the relative volumes occupied by the three types of crystallites are unequal. The magnetization is always very far from saturation, even in an applied field of 3.10⁴Oe, demonstrating the existence of a very large anisotropy energy in each of the tetragonal phases. We have measured the magnetization along the three axes originally fourfold, the three axes originally twofold, one axis originally threefold, and torque curves, in different magnetic fields. All measurements are in agreement with emu/cm³and ergs/cm³. Such very large anisotropy energy is the largest one known to us at room temperature for a ferromagnet, and we think that it is responsible for the disagreement between magnetic data previously published on this material.