Temperature Dependence of Spontaneous Magnetization in Superparamagnetic Nickel

摘要

The possibility of an anomalous temperature dependence of the spontaneous magnetization of superparamagnetic particles has been the subject of several investigations which are in contradiction. We have investigated nickel particles in the 30–100 A diameter range. These were prepared on silica gel supports in the manner familiar in contact catalysis. The spontaneous magnetization in these small particles is slightly but measurably lower than that of massive nickel. The calculated Curie temperature of a sample with average particle diameter of 30 A was about 565°K. It proved impossible to confirm the large variations of Curie temperature, strongly dependent on particle size reported recently for similar preparations.