Chemical Ordering and Microstructure of FePd Thin Films with perpendicular Magnetic Anisotropy
- PDF / 994,840 Bytes
- 13 Pages / 612 x 792 pts (letter) Page_size
- 59 Downloads / 208 Views
Chemical Ordering and Microstructure of FePd Thin Films with perpendicular Magnetic Anisotropy Gilles B.1, Xu F.F.2, Halley D., Marty A., Samson Y., Patrat G.3 DRFMC/SP2M/NM, CEA Grenoble Cedex 9, 38054 France 1 LTPCM-ENSEEG, BP 75, 38402 St Martin d'Hères, France 2 present address: ABS, National Institute for Research of Inorganic Materials (NIRIM), 1Namiki, Tsukuba, Ibaraki 305-0044, Japan 3 Laboratoire de Cristallographie du CNRS, BP 166, 38042 Grenoble Cedex 9, France ABSTRACT FePd(001) thin films have been grown by the molecular beam epitaxy (MBE) technique. At room temperature, these films are chemically disordered whereas at 350 °C a well ordered L10 structure is found with the c-axis oriented in the growth direction. By combining RHEED, STM and Auger measurements, it is suggested that ordering occurs at the growing surface by the development of bi-atomic steps of the ordered structure. We have put in evidence that the surfactant behavior of the Pd atoms is mainly involved in the ordering process and selects the single orientation of the c-axis. For intermediate temperatures between RT and 350 °C, TEM and X-rays have evidenced a pseudo-periodic arrangement of anti-phased domains having a columnar shape. The variation of the long-range order parameter is related to the average size of these ordered domains. INTRODUCTION Intermetallic thin films of FePd, FePt or CoPt have recently attracted considerable interest due to their tetragonal L10 ordered phase (CuAu I-type) having high uniaxial magnetocrystalline anisotropy constants (Ku ~ 107 -108 ergs/cm3) with an "easy" magnetic c-axis. Such materials are candidates for ultrahigh density magnetic recording media [1]. However, thermal stability and write field constraints require Ku to be adjusted to a moderate value, not exceeding the write field capability of the head and being however high enough to ensure stability of the stored magnetic energy. Among other tetragonal ordered bi-metallic compounds, it appears then that FePd is an interesting material, with Ku = 1.8 107 erg/cm3 and Ms = 1100 emu/cm3 in the bulk [1]. Also, it has been shown that FePd thin films may be easily deposited by co-evaporation with the molecular beam epitaxy (MBE) technique. The c-axis develops only in the growth direction and the long-range order parameter S (see definition below) depends on the growth temperature, thus resulting in Ku values ranging from 0 for the disordered γ phase obtained at room temperature (RT) to nearly the bulk value for the well ordered L10 phase grown at 350 °C [2]. The magnetic properties of these films with perpendicular magnetic anisotropy have been described elsewhere [3-4]. This article is devoted to the structural investigation of films having different S long-range order. It will provide an attempt to explain the chemical ordering process which occurs during growth at intermediate temperatures between RT and 350 °C. In the first section, the correlation between the S parameter and the growth temperature will be studied. Great attention has been paid to th
Data Loading...
