Journal of Alloys and Compounds 475 (2009) 339–342 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom Magnetostriction properties of FePd thin films: Dependence on microstructure Wilfried Wunderlich ∗ , Keisuke Takahashi, Daiji Kubo, Yoshihito Matsumura, Yoshitake Nishi Tokai University, Faculty for Engineering, Materials Science Department, Hiratsuka-shi, Kitakaname 1117, 259-1292 Kanagawaken, Japan article info Article history: Received 25 February 2008 Received in revised form 4 July 2008 Accepted 4 July 2008 Available online 22 August 2008 Keywords: Magnetostriction Intermetallic phases Ordering Transmission electron microcopy (TEM) Thin films FePd abstract FePd-alloys as thin films are potential actuator materials due to their large magnetostriction. In this paper experiments and simulations of TEM and XRD diffraction patterns showed, that the L1 0 -ordering has no influence on the lattice parameter ratio c/a =1.37. The degree of long-range order is higher for the sputtering temperature of 573 K than of 423 K, but the magnetostriction is higher for thin films produced at 423 K. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Thin film FePd-alloys have recently attracted attention as mag- netic memory alloys as well as actuator materials or sensor materials due to their remarkable high magnetostriction, the elastic elongation in a magnetic field. Alloys in the range of Fe–49 at% Pd to Fe–58 at% Pd, which crystallize in the L1 0 structure [1], show a high magneto-crystalline anisotropy, the tetragonal c-axis being the easy axis of magnetization The long-range order (LRO) parameter S decreases with increasing annealing temperature [2] and annealing of bulk specimens at 733 K for 15 h leads to S = 0.71 [3]. Recent stud- ies showed that the order parameter is further drastically reduced, when the grain size drops below 8 nm [4]. In a two-phase alloy the effect of the order parameter has to be distinguished from the effect resulting from the volume fraction of the two-phases [5]. Thin film growth of FePd [3,6] is most desirable for applications. According to Thornton’s model of thin film growth [7] especially the region below the recrystallization temperature T/T M = 0.5 (T = substrate temperature, T M = melting temperature, both in K) avoids growth defects and is most suitable to achieve good magnetic properties due to ordering. It is well accepted that the L1 0 -ordering is accom- panied by magnetic domain ordering and increases the magnetic susceptibility [3]. It is known that nano-particles prevent magnetic domains from changing their direction or size [4,8]. Magnetostric- ∗ Corresponding author. Tel.: +81 90 7436 0253; fax: +81 463 50 2096. E-mail address: wi-wunder@rocketmail.com (W. Wunderlich). Fig. 1. XRD diffraction pattern of the thin films produced at (a) 573 K (above) and (b) 423 K (below). The dark dots mark the peak positions due to the superstructure. An increasing c/a ratio lead to stronger degeneration of the peak positions as marked by the dotted lines in the simulation results. (For a clear display the height of the simulated {101} peak is reduced.) The vertical dashed line and the dots mark the superstructure with c/a = 1.37. 0925-8388/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2008.07.041