Mössbauer spectroscopy and magnetic properties of copper-304 stainless steel multilayer films

Abstract

The magnetic behavior of multilayer films of Cu-304 stainless steel (304SS) with equal layer thickness fabricated by magnetron sputtering at ambient temperature is reported. For small layer thickness (t=0.5–1.0 nm), the films show epitaxial fcc growth of 304SS on fcc copper, and multilayers are nonmagnetic due to nonmagnetic nature of fcc 304SS. For larger layer thickness (t=1.0–50.0 nm), 304SS grows epitaxially as fcc near the copper interface accompanied by a bcc 304SS growth away from the interface. As a result, two regimes are observed in 1.0–50.0 nm thickness range. Medium layer thickness (t=1.0–1.35 nm) multilayers show weak ferromagnetism characterized by small magnetization due to comparable thickness of ferromagnetic bcc 304SS and nonmagnetic fcc 304SS. A strong ferromagnetic behavior is observed for thick samples (t=1.35–50.0 nm) due to 304SS layer being primarily ferromagnetic bcc phase with very small percentage of fcc near the interface. Mössbauer effect spectroscopy and magnetometry were utilized to observe these magnetic phases. We present the dependence of magnetization on external field at room temperature for the multilayers. In Mössbauer measurements a single absorption peak for nonmagnetic films is observed. A superposition of a six-peak spectrum and a single-peak spectrum representing the existence of ferromagnetic and nonmagnetic phases in each layer were observed for all other films.