High-Coercivity Spin Glasses in Anisotropic Mo <sub>2</sub> FeB <sub>2</sub> -Type M <sub>1.5</sub> Mn <sub>1.5</sub> B <sub>2</sub> (M = Mo, W)

Magnetic materials combining spin-glass behavior with hard-magnet coercivity are important for fundamental and applied research. Herein, we report spin-glass behaviors coupled to remarkably large intrinsic coercivity values of 302.4 kA/m (<i>H</i><sub>c</sub> = 3.80 kOe) in Mo<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub> and 175.1 kA/m (<i>H</i><sub>c</sub> = 2.20 kOe) in W<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub>. Both phases belong to the Mo<sub>2</sub>FeB<sub>2</sub>-type structure known for enabling excellent structural properties and predicted altermagnetic candidates. Single-phase products were obtained via a compositionally tuned solid-state route that resolves prior phase-purity challenges. Temperature-dependent susceptibility measurements revealed spin-glass behavior below the freezing temperatures <i>T</i><sub>g</sub> = 29 K for Mo<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub> and <i>T</i><sub>g</sub> = 43 K (reentrant cluster spin glass) as well as a ferromagnetic (FM) transition at 70 K for W<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub>. AC susceptibility (χ') measurements exhibited frequency-dependent peaks that shifted to higher temperatures with increasing frequency, confirming the presence of dynamic spin freezing in both compounds. DFT calculations confirmed the presence of strongly competing FM and antiferromagnetic (AFM) interactions leading to competing FM, AFM and ferrimagnetic (FiM) orderings with a greater spin-exchange energy (Δ<i>E</i><sub>ex</sub> = 28-98 meV/f.u.) for FiM/AFM compared to FM in Mo<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub> and even greater Δ<i>E</i><sub>ex</sub> = 53-131 meV/f.u. in W<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub>. The magnetocrystalline anisotropy energy (MAE) is uniaxial, favoring the <i>c</i>-axis, with MAE = -0.17 meV/f.u. (Mo) and -0.10 meV/f.u. (W), which align well with the large hysteresis found experimentally, while the unexpectedly larger coercivity of Mo<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub> correlates with its greater AFM interactions. These findings enable the development of Mo<sub>2</sub>FeB<sub>2</sub>-type multifunctional materials, expanding their applications beyond traditional structural material properties.

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Journal
Journal of the American Chemical Society
Published
2025-10-27
DOI
https://doi.org/10.1021/jacs.5c12552
Primary Topic
Metallic Glasses and Amorphous Alloys
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article
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article

High-Coercivity Spin Glasses in Anisotropic Mo 2 FeB 2 -Type M 1.5 Mn 1.5 B 2 (M = Mo, W)

Alexei А. Belik, Boniface P. T. Fokwa, Takao Mori, Shola E. Adeniji
Journal of the American Chemical Society
Metallic Glasses and Amorphous Alloys
article

High-Coercivity Spin Glasses in Anisotropic Mo 2 FeB 2 -Type M 1.5 Mn 1.5 B 2 (M = Mo, W)

Alexei А. Belik, Boniface P. T. Fokwa, Takao Mori, Shola E. Adeniji
article en

Abstract

Magnetic materials combining spin-glass behavior with hard-magnet coercivity are important for fundamental and applied research. Herein, we report spin-glass behaviors coupled to remarkably large intrinsic coercivity values of 302.4 kA/m (<i>H</i><sub>c</sub> = 3.80 kOe) in Mo<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub> and 175.1 kA/m (<i>H</i><sub>c</sub> = 2.20 kOe) in W<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub>. Both phases belong to the Mo<sub>2</sub>FeB<sub>2</sub>-type structure known for enabling excellent structural properties and predicted altermagnetic candidates. Single-phase products were obtained via a compositionally tuned solid-state route that resolves prior phase-purity challenges. Temperature-dependent susceptibility measurements revealed spin-glass behavior below the freezing temperatures <i>T</i><sub>g</sub> = 29 K for Mo<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub> and <i>T</i><sub>g</sub> = 43 K (reentrant cluster spin glass) as well as a ferromagnetic (FM) transition at 70 K for W<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub>. AC susceptibility (χ') measurements exhibited frequency-dependent peaks that shifted to higher temperatures with increasing frequency, confirming the presence of dynamic spin freezing in both compounds. DFT calculations confirmed the presence of strongly competing FM and antiferromagnetic (AFM) interactions leading to competing FM, AFM and ferrimagnetic (FiM) orderings with a greater spin-exchange energy (Δ<i>E</i><sub>ex</sub> = 28-98 meV/f.u.) for FiM/AFM compared to FM in Mo<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub> and even greater Δ<i>E</i><sub>ex</sub> = 53-131 meV/f.u. in W<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub>. The magnetocrystalline anisotropy energy (MAE) is uniaxial, favoring the <i>c</i>-axis, with MAE = -0.17 meV/f.u. (Mo) and -0.10 meV/f.u. (W), which align well with the large hysteresis found experimentally, while the unexpectedly larger coercivity of Mo<sub>1.5</sub>Mn<sub>1.5</sub>B<sub>2</sub> correlates with its greater AFM interactions. These findings enable the development of Mo<sub>2</sub>FeB<sub>2</sub>-type multifunctional materials, expanding their applications beyond traditional structural material properties.

Journal of the American Chemical SocietyVol. 147(44)
University of Tsukuba (JP), National Institute for Materials Science (JP), University of California System (US)
Openalex Percentile: Top 68%
Metallic Glasses and Amorphous Alloys
DOISourceOpenAlex
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