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ANNUAL ISSUE

EARLY CAREER SCHOLARS IN MATERIALS SCIENCE

Structural and magnetic properties of FeCoMnCrSi multi-principal alloy Rahul Jangid1, Kenneth B. Ainslie1, Roopali Kukreja1,a) 1

Department of Materials Science and Engineering, University of California Davis, Davis, California 95616, USA Address all correspondence to this author. e-mail: [email protected] This paper has been selected as an Invited Feature Paper. a)

Received: 16 October 2019; accepted: 13 December 2019

In this study, the magnetic properties of Fe39.8Co19.92Mn20.52Cr14.77Si5 multi-principal element alloy in both bulk and thin films were studied. X-ray diffraction measurements show coexisting face centered cubic (FCC) and hexagonal close packed phases in the bulk and the 500 nm thin films, while only FCC phase is observed in the 65 nm thin film. A four orders of magnitude increase in the magnetic moment is observed for 65 nm thin film compared with the bulk sample. Evolution of magnetization as a function of temperature and applied magnetic field shows multiple magnetic transitions. A paramagnetic to spin glass transition is detected at TS ∼ 390 K for all samples. Further cooling results in a spin glass to ferromagnetic (FM) transition, and the transition temperature, TF, is dependent on the film thickness. Higher saturation magnetization and transition temperature observed for the thin film samples indicate the stabilization of FM ordering due to thickness confinement.

Roopali Kukreja

Roopali Kukreja joined Materials Science and Engineering Department at UC Davis as an assistant professor in fall 2016. She received her B.S. in Metallurgical Engineering and Materials Science from the Indian Institute of Technology, Bombay, in 2008 and then her M.S. and Ph.D. degrees in Materials Science and Engineering from Stanford University in 2011 and 2014, respectively. Prior to her appointment at UC Davis, Kukreja worked as a postdoctoral researcher at the UC San Diego, with Profs. Oleg Shpyrko (Physics Department) and Eric Fullerton (Center for Magnetic Recording Research). Her research interests are imaging dynamics in magnetic and electronic materials. The main focus is on understanding and manipulating the switching in magnetic materials and phase transitions in metal–insulator materials on femtosecond timescales and nanometer length scales. Recently, her group has also started working on understanding magnetic properties of MPEAs and correlating it to structural properties. Her group utilizes reactive and magnetic sputtering for thin film growth and advanced X-ray characterization techniques, including X-ray spectroscopy, coherent Xray scattering, and X-ray imaging various synchrotron sources for performing detailed characterization of magnetic and electronic materials. She is the recipient of Melvin P. Klein Scientific Development Award (2015), AFOSR Young Investigator Award (2018), and Nuclear Regulatory Commission Faculty Development Scholar (2019).

Introduction In the last decade, multi-principal element alloys (MPEAs) have attracted a great deal