Local magnetic correlations and light-sensitive centers in the Cr2AlC MAX phase

Malgorzata Wierzbowska; Anna Basa; Kazuhiro Marumoto; Jiaxi Wang; Katarzyna Gas; Maciej Sawicki; Kacper Sierakowski; Karel Carva; Michal Bockowski

arXiv · 2607.15110

Local magnetic correlations and light-sensitive centers in the Cr2AlC MAX phase

Malgorzata Wierzbowska·Anna Basa·Kazuhiro Marumoto·Jiaxi Wang·Katarzyna Gas·Maciej Sawicki·Kacper Sierakowski·Karel Carva·Michal Bockowski

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Abstract

Cr2AlC MAX phase is synthesized by high-pressure solid-state annealing and investigated as a candidate platform for optically responsive magnetism. Structural characterization confirms the formation of the Cr2AlC phase, while magnetic and optical-magnetic properties are examined by superconducting quantum interference device (SQUID) magnetometry, electron spin resonance (ESR), and first principles calculations. SQUID magnetometry identifies Cr 2AlC as a weak, field-linear metallic paramagnet dominated by Pauli-like susceptibility of itinerant Cr-derived states. Its non-monotonic temperature dependence is described by an additional contribution from antiferromagnetically coupled Cr-Cr dimers, whereas the low-temperature Curie-like upturn originates from only a trace population of localized Cr centers. Under red-light illumination, SQUID magnetometry does not reveal an intrinsic macroscopic optomagnetic response. In contrast, ESR at 4 K shows a reversible light-induced reduction of a local magnetic signal, but the optically modified spin population corresponds only to several tens of ppm of the Cr sublattice. Ab initio Bethe-Salpeter equation (ai-BSE) calculations combined with the maximally localized Wannier function analysis suggest that optical excitation can redistribute spin polarization between neighboring Cr sites with the opposite local moments. The combined experiment-theory approach therefore establishes the hierarchy of magnetic contributions in Cr 2AlC and identifies the microscopic origin of its local optical sensitivity. This provides a reference for designing MAX phases and related MXenes in which defects, surface terminations or reduced dimensionality may enhance optically active magnetic states.

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Malgorzata Wierzbowska, Anna Basa, Kazuhiro Marumoto, Jiaxi Wang, Katarzyna Gas, Maciej Sawicki, Kacper Sierakowski, Karel Carva, Michal Bockowski. 2026-07-16. Local magnetic correlations and light-sensitive centers in the Cr2AlC MAX phase. https://arxiv.org/abs/2607.15110

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