Moessbauer study on epitaxial CO_xFe_(4-x)N films grown by molecular beam epitaxy

摘要

We prepared Co_xFe_(4-x)N (x = 0, 1, 3) films on SrTiO_3(STO)(001) substrates by molecular beam epitaxy. The epitaxial relationship with Co_xFe_(4-x)N[100](001) || STO[100](001) was confirmed by ω-29 (out-of-plane) and φ-2θ_x (in-plane) x-ray diffraction (XRD) measurements. The degree of order of atoms (S) in the Co_xFe_(4-x)N films was estimated to be ～0.5 by the peak intensity ratio of Co_xFe_(4-x)N(100) (superlattice diffraction line) to (400) (fundamental diffraction line) in the φ-2θ_x XRD patterns. Conversion electron Moessbauer spectroscopy studies for the Co_xFe_(4-x)N films revealed that some N atoms are located at interstitial sites between the two nearest corner sites in the Co_xFe_(4-x)N films, and/or Fe atoms are located at both the corner and face-centered sites in the CoFe_3N and Co_3FeN films. In order to realize high spin-polarized Co_xFe_(4-x)N films having large S, further optimization of growth condition is required to prevent the site-disorders.