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DOE OSTI · 2571359

MnBi 2 Is a Permanent Magnet

Badding, Catherine K. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)] (ORCID:0000000204485493)·Riesel, Eric A. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)]·Murphy, Ryan A. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)]·Puggioni, Danilo [Northwestern Univ., Evanston, IL (United States)] (ORCID:0000000221284191)·Popov, Dmitry [Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)]·Fabbris, Gilberto [Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)] (ORCID:0000000182784985)·Haskel, Daniel [Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)] (ORCID:0000000255325908)·Rondinelli, James M. [Northwestern Univ., Evanston, IL (United States)] (ORCID:0000000305082175)·Altman, Alison B. [Texas A&M Univ., Kingsville, TX (United States)] (ORCID:0000000249755004)·Freedman, Danna E. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)] (ORCID:0000000225798835)
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Abstract

Creating and understanding new permanent magnets requires an understanding of the impact of orbital angular momentum on coercivity. A simple approach to interrogating this relationship is by incorporating high Z (where Z is the atomic number) elements into binary compounds to maximize spin–orbit coupling. The Mn–Bi system is an appealing platform for these studies since it contains MnBi, a permanent magnet with a large coercive field. We previously identified a new compound in the Mn–Bi system, MnBi 2 , but could not elucidate its magnetic properties ex situ due to its decomposition upon decompression. Here, we harnessed synchrotron X-ray magnetic circular dichroism to probe the magnetism of MnBi 2 at high pressure within a diamond anvil cell. Our results indicate that MnBi 2 exhibits ferromagnetic hysteresis at both 10 K and room temperature. Through calculations and experiments, we show that orbital angular momentum and spin–orbit coupling from Bi impart magnetic anisotropy in MnBi 2 . Comparing the Mn–Bi family of compounds, we consider the Bi p and d orbitals to explain the differences in magnetic behavior within the system. Collectively, these results validate leveraging high-Z elements in the synthesis of new hard permanent magnets.

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRYHigh pressureMagnetismPermanent MagnetsX-ray Dichroism

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Badding, Catherine K. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)] (ORCID:0000000204485493), Riesel, Eric A. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)], Murphy, Ryan A. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)], Puggioni, Danilo [Northwestern Univ., Evanston, IL (United States)] (ORCID:0000000221284191), Popov, Dmitry [Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)], Fabbris, Gilberto [Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)] (ORCID:0000000182784985), Haskel, Daniel [Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)] (ORCID:0000000255325908), Rondinelli, James M. [Northwestern Univ., Evanston, IL (United States)] (ORCID:0000000305082175), Altman, Alison B. [Texas A&M Univ., Kingsville, TX (United States)] (ORCID:0000000249755004), Freedman, Danna E. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)] (ORCID:0000000225798835). 2025-07-15. MnBi 2 Is a Permanent Magnet. https://doi.org/10.1021/jacs.5c06874

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