Mössbauer investigation of Fe 1−x Cr x films grown by ion-beam sputter deposition

Abstract

Fe 1− x Cr x ( 0 < x < 0.70 ) films, 220 nm thick, on Si and fused-SiO 2 substrates were prepared using ion-beam sputter deposition, and their structural properties were determined by 57Fe conversion electron Mössbauer spectroscopy (CEMS) and X-ray diffraction experiments (XRD) at room temperature. CEM spectra show magnetic ordering for 0< x⩽0.28, and the BCC α-phase is evidenced through XRD diagrams in all cases. The general trend for the films is that the average hyperfine magnetic field (HMF) values are lower compared to bulk counterparts. Moreover, a parabolic change in average HMF with Cr content x could be established. For 0.32⩽ x<0.70, the CEM spectra exhibit a pseudo-single line, which denotes paramagnetic state. Between x = 0.32 and x = 0.38 , there exists a multiphase region where the alloys mainly consist of α and δ (A15-type) phases. Then, in the concentration range x=0.38–0.58, the films only display the metastable δ-phase. For 0.58⩽ x⩽0.66, there appears a new transition region where α- and δ-phases coexist. Finally, the domain of the paramagnetic α-phase alone stretches from x = 0.66 to at least x = 0.70 . Emphasis is placed on the metastable δ-phase which appears over a wide monophase region. Particularly, the site occupancy could be determined through the CEM spectrum for x = 0.49 .