On the path towards ferromagnetic MAX phases: Synthesis of (V1-xCrx)2GaC, a Pauli paramagnet almost matching the Stoner criterion

N. Kubitza, R. Xie, I. Tarasov, C. Shen, H. Zhang, U. Wiedwald, C. S. Birkel
Chem. Mater. 2023.
DOI: 10.1021/acs.chemmater.3c00591 (opens in new tab)

MAX phases that exhibit long-range magnetic order in the bulk are still very hard to synthesize. Chromium and manganese are the cut-off elements when transitioning through the 3d metals that still form stable full and doped MAX phases, respectively. An iron-based (on the M-site) bulk MAX phase does not exist. Therefore, other strategies to induce long-range magnetic ordering in bulk MAX phases are necessary to open the path to new functional materials. Here, we demonstrate the non-conventional synthesis of a hitherto unknown MAX phase solid-solution (V1-xCrx)2GaC by microwave heating. The full series with 0 < x < 1 (x = 0.20, 0.40, 0.50, 0.60, 0.80) forms almost single phase with minimal differences in their morphology. Their magnetic properties, however, differ rather significantly with a maximum susceptibility around x = 0.80. Both the experimental and theoretical/ab initio magnetic analysis confirm that the solid-solution (V1-xCrx)2GaC is an itinerant Pauli paramagnet, that almost fulfils the Stoner criterion for ferromagnetic order (for compositions with x around 0.80). This is a powerful insight into how chemical composition couples with electronic structure and the resulting bulk magnetic properties because it provides crucial guidelines to produce long-range ordered magnetic MAX phases.