Complex magnetism of single-crystalline AlCoCrFeNi nanostructured high-entropy alloy

Primož Koželj; Andreja Jelen; Goran Dražić; Stanislav Vrtnik; Jože Luzar; Magdalena Wencka; Anton Meden; Michael Feuerbacher; Janez Dolinšek

doi:10.1016/j.isci.2023.106894

Complex magnetism of single-crystalline AlCoCrFeNi nanostructured high-entropy alloy

iScience. 2023 May 18;26(6):106894. doi: 10.1016/j.isci.2023.106894. eCollection 2023 Jun 16.

Authors

Primož Koželj^{1

2}, Andreja Jelen¹, Goran Dražić³, Stanislav Vrtnik¹, Jože Luzar¹, Magdalena Wencka^{1

4}, Anton Meden⁵, Michael Feuerbacher⁶, Janez Dolinšek^{1

2}

Affiliations

¹ Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
² University of Ljubljana, Faculty of Mathematics and Physics, Jadranska 19, SI-1000 Ljubljana, Slovenia.
³ National Institute of Chemistry, Department of Materials Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia.
⁴ Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, PL-60-179 Poznań, Poland.
⁵ University of Ljubljana, Faculty of Chemistry and Chemical Technology, Večna Pot 113, SI-1000 Ljubljana, Slovenia.
⁶ Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.

Abstract

We have investigated magnetism of the Al₂₈Co₂₀Cr₁₁Fe₁₅Ni₂₆ single-crystalline high-entropy alloy. The material is nanostructured, composed of a B2 matrix with dispersed spherical-like A2 nanoparticles of average diameter 64 nm. The magnetism was studied from 2 to 400 K via direct-current magnetization, hysteresis curves, alternating-current magnetic susceptibility, and thermoremanent magnetization time decay, to determine the magnetic state that develops in this highly structurally and chemically inhomogeneous material. The results reveal that the Cr-free B2 matrix of composition Al₂₈Co₂₅Fe₁₅Ni₃₂ forms a disordered ferromagnetic (FM) state that undergoes an FM transition at $T_{C} \approx$ 390 K. The Al- and Ni-free A2 nanoparticles of average composition Co₁₉Cr₅₆Fe₂₅ adopt a core-shell structure, where the shells of about 2 nm thickness are CoFe enriched. While the shells are FM, the nanoparticle cores are asperomagnetic, classifying into the broad class of spin glasses. Asperomagnetism develops below 15 K and exhibits broken-ergodicity phenomena, typical of magnetically frustrated systems.

Keywords: Entropy; Magnetism; Materials science.