Magnetic properties of substitutional solid solutions of nickel and iron hexacyanoferrate–hexacyanochromate

Abstract

In order to evaluate the influence of substitution at the central metal ion position in transition hexacyanometallates in some detail, the magnetic studies were carried out on a series of solid solutions of metal hexacyanometallates of the composition M[Fe^II(CN)₆]_{1− x} [Cr^III(CN)₆]_x, where M = Ni^II and Fe^III. The temperature and field dependences of magnetization were studied using a superconducting quantum interference device magnetometer. The field dependence of the samples at 5 K shows a hysteresis behaviour. For M = Ni^II, the transition temperature increases with increase in the substitution of low-spin Fe(III) by Cr(III) in the hexacyanometallate unit. The saturation magnetization was found to decrease with increase in the iron concentration. The observed variation in the magnetic properties, such as the value of T_C and the nature of magnetic ordering, is attributed to the variation in the composition of the transition-metal ion in the coordination sphere of carbon. On the other hand, for M = Fe^III, the transition temperature and saturation magnetization remained almost unchanged, indicating that substitution at the carbon coordination site did not produce any change in the magnetic interaction among the transition-metal ions through the cyanide ions.