HEAT CAPACITIES AT LOW TEMPERATURES, ENTROPY AND ENTHALPY INCREMENTS OF FOUR NICKEL ZINC FERROSPINELS MOLECULAR FIELD FLUCTUATION EFFECTS IN MIXED NICKEL ZINC FERRITES LOW TEMPERATURE HEAT CAPACITY AND THERMODYNAMIC PROPERTIES OF ZINC FERRITE

摘要

The heat capacity and the magnetic moment versus temperature of ZnxNil-x Fe204 has been measured from about 4°K to 300°K where x = .9, .8, .7, and .6. The heat capacity has been measured over the same temperature range for Zn Fe2O4. An antiferromagnetic cooperative transition at about 9.5°K was observed in ZnFe204 which gradually becomes more rounded and contributes less entropy as x decreases. The magnetic moment decreases gradually with increasing temperature and for the larger values of x goes slowly towards zero in marked contrast to the usual Curie temperature behavior. The results are interpreted as being due to molecular field fluctuations. Predicted thermal effects due to triangular-ferrimagnetic transitions were not found. This result is also interpreted in terms of molecular field fluctuations.