Magnetic properties of hematite single crystals

Abstract

Abstract An experimental study of natural and synthetic single crystals of hematite containing small quantities of impurities was made to establish what effect impurities had on a variety of magnetic properties. In both types of crystals the average values for the weak magnetic moment were comparable regardless of the impurity. A triaxial anisotropy was observed in the basal plane of many natural crystals and for the samples with the largest anisotropy the major impurity was found to be Sn; this was also the only impurity which induced a triaxial anisotropy in the synthetic crystals. The coercive force was also much larger in the natural and synthetic crystals containing Sn. The transition temperature was found to be progressively lowered by increasing the amounts of certain impurities but the values for this temperature in synthetic and natural crystals containing the same impurities were often different. For the synthetic crystals, small additions of Sn depressed the transition temperature to a greater degree than an equivalent amount of any of the other impurities. In the region of the low temperature transition a large change in the value of differential susceptibility with temperatures was observed for both pure and impure crystals.