Structural and magnetic characteristics of FeCo thin films modified by combinatorial ion implantation

Abstract

This work presents results on modifications of the structure and the magnetic properties of magnetron-sputtered Fe 50Co 50 films induced by high dose Sm or Xe ion implantation. A combinatorial approach was used in order to screen a wide range of implantation doses from 4 × 10 15 to 1.6 × 10 17 ions/cm 2. Sm-implanted FeCo films are considered as precursors for the synthesis of multi-phase exchange-spring magnetic materials while Xe ion implantation of such films is known as a method to modify film stresses and magnetical properties. Materials libraries of as-implanted films were investigated by energy dispersive X-ray analysis (EDX) and secondary ion mass spectrometry (SIMS) for the film composition and concentration depth profiles, transmission electron microscopy (TEM) and X-ray diffraction (XRD) for the film morphology and crystalline structure, vibrating sample magnetometry (VSM) for the magnetization behaviour and four-point probe measurements for the film resistivity. Three main results were found on the basis of this combinatorial study: (i) The high-dose Sm-implanted samples have an overall Sm concentration above the value necessary for Sm-Fe(Co) alloy formation and show magnetic hysteresis curves corresponding to two-phase or two-layer film stucture; (ii) The two implanted series show quite different magnetic anisotropy in the film plane — a negligable one for Xe and a strong one for Sm implantation; (iii) For the Sm-implanted samples a clear local maxima in the coercivity H c and the anisotropy field H k can be seen at D Sm ≥ 1 × 10 16 ions/cm 2. The XRD spectra of the libraries show that the last two effects are closely related to the film strains introduced by the implantation process.