Pinning energy of domain walls in MnZn ferrite films

The growth of magnetically soft ferrite thin films, particularly Mn-Zn ferrite, is motivated by potential applications [1, 2]. Given their low conductivity, they are used for high frequency applications. For op-timum performance at these high frequencies also, their magnetic hysteresis should be as low as possible. This last property is related to domain wall motion, and several studies have been performed on the do-main structure of poly-crystalline MnZn and NiZn ferrites, and their relationship to the average grain size [3, 4]. It is known that due to low magneto-crystalline anisotropy of certain MnZn- ferrite compositions, the domain wall size can be in the order of 1 µm; so the grain size domain can be varied from below to above the domain wall size [5]. In the first case, the grains are mono-domain, and their behavior is radi-cally different to the multi-domain case. This critical grain size, Lc, for the MnZn ferrites has been re-ported as 4µm [5]. In samples of several magnetic materials, with grain size L< Lc the magnetic suscep-tibility results, and coercivity behavior indicated the absence of domain walls in these small grains [6]. The magnetic quality of ferrite films is also mainly dependent on the extrinsic properties, e.g. morpho-logical properties like mono and multidomain structures, grain size distribution, grain boundary, and defects. The properties above have a direct influence on some parameters of the hysteresis behavior; especially the coercive field is highly sensible to the above mentioned properties. The hysteresis beha-vior of magnetically soft ferrite can be fitted well to the Jiles-Aterton Model (JAM)[7, 8]. Such a proce-