The permeability of ferrite plated films

Abstract

Recently, there has been a growing interest in the fabrication of ferrite films, especially by pulsed laser deposition (PLD), e.g [I], but also by sputtering, see for instance [Z]. Owing to their insulating character ferrite films could be applied for integrated inductors 111 or to improve the efficiency of thin film recording heads 131. Most of the studies of the growth of ferrite films, thus far, only report the saturation magnetization value, Ms, or the coercivity, He. However, in mast applicatons the permeability of the ferrite films is the key parameter, which unfortunately is rarely reported [2]. A disadvantage of the films grown by PLD or sputtering is that they require a high deposition temperature of typically around 650 'C, which is too high for most application in devices which involve other thin layers. Ferrite films grown by ferrite plating offer a much more favourable depostion temperature of only 80 'C [4]. We will discuss the characterization of the magnetic properties, notably permeability's of NiZn-ferrite plated films. The approx. 1 pm thick NiZn-ferrite films studied had a Ms % 520 kA/m which is comparable to bulk values for NiZn-ferrite. As can be seen from Fig. 1, the NiZn-ferrite films grown by ferrite plating on a glass substrate have a p = 28 f 3 (open balls). This value can be increased to p= 60 *5 hy an anneal step at T 2 325 OC, which in addition increases