Frequency dependence of the complex permeability of monocrystalline MnZn ferrous ferrites

Abstract

For recording head applications it is important to know the response of monocrystalline MnZn ferrous ferrites to signals of various frequencies. For this purpose the complex permeability μ̄ = μ′−jμ″ of these materials has been studied using alternating magnetic fields with small amplitude and frequencies up to a few MHz. At 60 kHz, 0.5 MHz and 4.5 MHz the temperature dependence of μ′ and μ″ has been investigated for a wide range of temperatures T, including the temperature where μ′(T) reaches its so-called secondary maximum due to anisotropy compensation by the ferrous ions. An interesting feature found is that when the frequency f is raised this secondary maximum inverts to a minimum. In addition, μ′(f) and μ″(f) have been studied at some selected temperatures. For the case of a [100] preferential direction of the magnetization an empirical expression was obtained for μ′(f).