Temperature Dependence of YIG Magnetization

The temperature dependence of the saturation magnetization, 4πM, has been measured for pure, polished YIG spheres in the temperature range from 4–50°K. The technique used involved measuring the magnetic field separation of the 210 and 220 magnetostatic modes as a function of temperature. The mode spacing is equal simply to 4πM/5. This method offers a high degree of precision since the linewidths are less than 1 gauss and the separation of the two modes is the order of 500 gauss. Data were taken for several samples and with the external magnetic field oriented in both the [100] and [111] directions. The experimental results have been fitted to the theoretical expression of Dyson. Only the first-order correction term to Bloch's equation was necessary, the result being M=M0(1−8.19×10−6T32−1.03×10−7T52). A fit to the T32 term alone is definitely excluded.