ANOMALOUS ELECTRICAL PROPERTY OF COSIF6.6H2O NEAR ITS TRANSITION-TEMPERATURE

The electrical resistance of the CoSiF6.6H2O crystal along its three axes and of the powdered material has been measured in the vicinity of the transition temperature. The resistance of the crystal passes through a peak at 246K, the transition temperature in the cooling cycle, during heating the resistance jumps to a much lower value at about 265K. At and above 265K in the heating cycle the DC (i- nu ) characteristics show non-linear variation. A spontaneous voltage of approximately 0.6 V, of opposite polarity to the applied voltage, is developed across the crystal after a current of a few milliamperes is passed through the crystal via Aquadag electrodes and the applied voltage withdrawn. The value of the spontaneous voltage depends on the electrode material and the temperature. The non-linearity in the (i- nu ) characteristics is absent when AC measurements are made. The powdered sample does not show any anomaly in its resistance.