Temperature dependence of core losses at high frequency for MnZn ferrites

The core losses (P-L) of MnZn ferrites prepared by a solid-state reaction method were investigated as a function of magnetic induction and frequency (P-L = kB(m)(x)f(y)). The exponent (x) of magnetic induction was 2.58 at 1000 kHz and 2.01 at 3000 kHz, and the exponent (y) of frequency was 2.22 at 30 mT and 2.73 at 10 mT. The core losses (P-L) were divided into hysteresis loss (P-h), eddy current loss (P-e) and residual loss (P-r). Each loss contribution was discussed to be dependent on temperature. P-h decreased monotonically with increasing temperature. P-e firstly decreased with increasing temperature, minimized at 100 degrees C, and then increased. As the temperature increased, the imaginary permeability at MHz was significantly enhanced and the resonance frequency (f(r)) decreased. The increase in P-r with increasing temperature should be attributed to the decreasing f(r) which is due to the resonance in the domain wall caused by high speed rotation of spin inside the domain. (C) 2009 Elsevier B.V. All rights reserved.