Extremely low frequency losses and thermal fluctuation after effect in soft ferrites

Abstract

Magnetic losses in soft magnetic ferrites have been measured at extremely low frequencies and high magnetic inductions. A logarithmic variation of losses per cycle with frequency has been found in a frequency range between 0.01 Hz and less than 100 Hz. This anomalous loss with frequency dependence is attributed to the thermal fluctuation after effect which yields the same anomalous losses in metallic soft magnetic materials. The after effect constant Sv has been calculated from this anomalous loss and the static and eddy current losses in soft ferrites have been discussed.