Temperature dependence of core loss in Co-substituted MnZn ferrites

Substitution of Co2+ for a small part of Fe2+ in (MnZn)Fe2O3 results in much smaller temperature variation in core loss, compared with that of conventional MnZn ferrite used for transformers. This effect appears in the temperature dependence of hysteresis loss rather than two other contributions of loss, eddy current loss, and residual loss. The total loss not exceeding 370 kW/m3 at 100 kHz/200 mT is obtained in the wide temperature range from 0 to 100 °C. However, excess substitution gives rise to a steep increase of loss below room temperature. Both the improvement of temperature dependence and the abrupt changes in loss in a lower-temperature region accompanying Co2+ substitution could result from a change in the magnetocrystalline anisotropy constant K1.