Ternary FeCrNi martensitic thin films sputtered on a flexible substrate from a single AISI 304 austenitic stainless steel source: Effect of deposition rate on structural and magnetic properties

Abstract

Abstract The effect of deposition rates on the structural and magnetic properties of the ternary FeCrNi martensitic thin films produced via a source material made of the commercial AISI 304 austenitic stainless steel was investigated. The films with 50 nm thickness were deposited on a flexible amorphous polymer substrate by using dc magnetron sputtering. As increasing deposition rate, the Fe and Ni contents of the films increased while the Cr component decreased confirming the same materials in the source. And, all films examined by X-ray diffraction have a body centred tetragonal structure confirming the martensitic state, and the peak intensities changed depending on the film content which was varied by deposition rate. Also, the morphological analysis of the surfaces performed by a scanning electron microscope (SEM) displayed that the smoothest surface were obtained at high deposition rates. Further measurements by an atomic force microscopy disclosed an increase in the film surface smoothness and a decrease in the values of roughness parameters confirming the SEM images. As to magnetic analysis, the increase of total of Fe and Ni contents resulted in an increase in saturation magnetization, MS. The MS values of films, were detected to increase from 991.0 to 1283.1 emu/cm3 with decreasing coercivity from 131 to 74 Oe as the deposition rate increased from 0.04 to 0.12 nm/s. In this study, the increase of the Fe and Ni components and smoothness in surfaces may give rise to the ternary FeCrNi martensitic thin films gain the softer magnetic properties with increasing deposition rate. A probable explanation to this results may come from the hysteresis loops; the change in the deposition rate produces an increase in the MS and remanent magnetization, Mr, and decrease in the coercivities which led to almost unchanged shape of the loops since the Mr/MS ratio is between 6.3 and 6.8. The ternary FeCrNi thin films produced by a magnetron sputtering technique have a martensitic phase, which indicates the soft ferromagnetic state without any further treatment. To our knowledge, this has not been expressed in previous relevant studies. It is seen that the magnetic properties of the ternary FeCrNi martensitic thin films can be easily controlled by changing production parameters for potential electric and electronic devices on flexible substrates.