Materials Science and Engineering B103 (2003) 233–240 A study of sputtering process for nanocrystalline FeAlN soft magnetic thin films Yungui Ma, Xiaohong Li, Tian Xie, Fulin Wei ∗ , Zheng Yang Research Institute of Magnetic Materials, Lanzhou University, Lanzhou 730000, China Received 22 November 2002; received in revised form 5 May 2003; accepted 2 June 2003 Abstract Nanocrystalline FeAlN thin films were successfully prepared by three ways: the growth of deposited nanocrystalline film by ex-situ process, in-situ process and controlling crystallization of deposited amorphous films. The magnetic properties and microstructure such as aspect and surface morphology were investigated. It is found that the FeAlN films by ex-situ process show the best soft magnetic properties: higher saturation and lower coercivity. The FeAlN films synthesized by controlling the crystallization of as-deposited amorphous films exhibit the highest thermal stability. © 2003 Elsevier B.V. All rights reserved. Keywords: Nanocrystalline FeAlN magnetic thin films; Sputtering; Amorphous films 1. Introduction As recording media coercivity increases to support higher recording densities, supplying adequate field to the media surface becomes a challenge. For example, to successfully write in a 5000–7000 Oe media, one should generate a field of least 2.0 T at the write head gap [1]. For this application a high saturation magnetization (B s ∼ 20 kG or bigger) is required for write head core materials. In addition, for suc- cessful head operation to high B s , the core material must have good soft magnetic properties: H c < 2.0 Oe, H k value in the 5–10 Oe range, permeability on the order of 1000, low internal stress and magnetostriction, and high resistiv- ity to be able to switch at high speed without serious eddy damping. It is well known that the basic conditions for good soft magnetic properties are low or vanishing magnetic anisotropy of a few J m -3 only [2]. Thus, the prerequisite for soft magnetic behavior is that the effective magnetocrys- talline anisotropy is low. Superior properties additionally require a low magnetostriction which reduces magnetoelas- tic anisotropy. Nanocrystalline FeXN thin films have been heavily in- vestigated as candidates for high moment pole materials of ∗ Corresponding author. Fax: +86-931-891-2837. E-mail address: weifl@lzu.edu.cn (F. Wei). write head [3–7], where X represents any of variety of al- loying elements including Ta, Hf, Nb, Zr, Si and Al. The soft magnetism in FeXN films originates from the incor- poration of interstitial N atoms, which are instrumental in refining -Fe grain structure [8]. The grain size is usually smaller than the ferromagnetic exchange length, L ex (=35 nm) [9], and the local magnetic anisotropy can be substan- tially lowered due to the strong exchange coupling between grains [10]. Based on alternative technologies, two different methods can be used to fabricate nanocrystalline soft mag- netic FeXN films. The widely used high temperature tech- nique is to anneal amorphous as-deposited FeXN alloy and develop a fine nanostructure. The soft magnetic properties can be improved through optimizing annealing parameters. A different design depends on direct growth of as-deposited, nanostructured soft magnetic FeXN films, again by sputter- ing. In this work, nanocrystalline FeAlN soft magnetic thin films were prepared by three ways and the microstructure and magnetic properties were investigated. 2. Experimental procedure The nanocrystalline soft magnetic FeAlN films were fabricated by following methods. a) The growth of ex-situ process. In this method, the nanocrystalline FeAlN films grew on water-cooled sub- 0921-5107/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0921-5107(03)00239-3