Aligned and exchange-coupled L10 (Fe,Co)Pt-based magnetic films

Authors

Yi Liu, University of Nebraska-LincolnFollow
Thomas A. George, University of Nebraska - LincolnFollow
Ralph Skomski, University of Nebraska-LincolnFollow
David J. Sellmyer, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

2012

Citation

JOURNAL OF APPLIED PHYSICS 111, 07B537 (2012); doi:10.1063/1.3679099

Comments

Copyright VC 2012 American Institute of Physics.

Abstract

Films of aligned L1₀-structure (Fe,Co)Pt with fcc Fe(Co,Pt) are synthesized by co-sputtering Fe, Co, and Pt on an (001) MgO substrate with in situ heating at 830 degrees C. The nanostructures and magnetic properties of the films are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID). The compositions of the samples (Fe,Co)_xPt_1-x are designed to maintain an atomic Fe: Co ratio of 65: 35 while increasing the Fe,Co content in each successive sample. In samples with low Fe and Co concentration, the XRD patterns exhibit three strong peaks, namely L1₀ (Fe,Co)Pt (001), L1₀ (Fe,Co)Pt (002), and MgO (002). A fourth peak is observed in samples with high Fe and Co concentration and identified as fcc (002). The XRD patterns confirm the formation of L1₀-ordered (Fe,Co)Pt and its epitaxial growth on MgO. TEM shows that the (Fe,Co)Pt films form isolated magnetic grains of about 100 nm in diameter. Hysteresis-loop measurements show that the increase of the Fe,Co concentration from 57.3 to 68.3 at% enhances the saturation magnetization M_s from 1245 emu/cm³ to 1416 emu/cm³, and the coercivity decreases from 32 kOe to 8.9 kOe. The nominal maximum energy product per grain is 64 MGOe.