Highly complex magnetic behavior resulting from hierarchical phase separation in AlCo(Cr)FeNi high-entropy alloys

Qianqian Lan; András Kovács; Jan Caron; Hongchu Du; Dongsheng Song; Sriswaroop Dasari; Bharat Gwalani; Varun Chaudhary; Raju V Ramanujan; Rajarshi Banerjee; Rafal E Dunin-Borkowski

doi:10.1016/j.isci.2022.104047

Highly complex magnetic behavior resulting from hierarchical phase separation in AlCo(Cr)FeNi high-entropy alloys

iScience. 2022 Mar 11;25(4):104047. doi: 10.1016/j.isci.2022.104047. eCollection 2022 Apr 15.

Authors

Qianqian Lan^{1

2}, András Kovács¹, Jan Caron¹, Hongchu Du^{1

3}, Dongsheng Song¹, Sriswaroop Dasari⁴, Bharat Gwalani⁴, Varun Chaudhary⁵, Raju V Ramanujan⁵, Rajarshi Banerjee^{4

5}, Rafal E Dunin-Borkowski¹

Affiliations

¹ Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany.
² School of Materials Science and Engineering, Tsinghua University, Beijing 100086, China.
³ Central Facility for Electron Microscopy, RWTH Aachen University, 52074 Aachen, Germany.
⁴ Department of Materials Science and Engineering, University of North Texas, Denton, TX 76201, USA.
⁵ School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.

Abstract

Magnetic high-entropy alloys (HEAs) are a new category of high-performance magnetic materials, with multicomponent concentrated compositions and complex multi-phase structures. Although there have been numerous reports of their interesting magnetic properties, there is very limited understanding about the interplay between their hierarchical multi-phase structures and the resulting magnetic behavior. We reveal for the first time the influence of a hierarchically decomposed B2 + A2 structure in an AlCo_0.5Cr_0.5FeNi HEA on the formation of magnetic vortex states within individual A2 (disordered BCC) precipitates, which are distributed in an ordered B2 matrix that is weakly ferromagnetic. Non-magnetic or weakly ferromagnetic B2 precipitates in large magnetic domains of the A2 phase, and strongly magnetic Fe-Co-rich interphase A2 regions, are also observed. These results provide important insight into the origin of coercivity in this HEA, which can be attributed to a complex magnetization process that includes the successive reversal of magnetic vortices.

Keywords: Condensed matter physics; Magnetism; Phase transitions.