Accessing new magnetic regimes by tuning the ligand spin-orbit coupling in van der Waals magnets.

Tartaglia, Thomas A; Tang, Joseph N; Lado, Jose L; Bahrami, Faranak; Abramchuk, Mykola; McCandless, Gregory T; Doyle, Meaghan C; Burch, Kenneth S et al. · Sci Adv · 2020

basic_science · Level V

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Abstract

Van der Waals (VdW) materials have opened new directions in the study of low dimensional magnetism. A largely unexplored arena is the intrinsic tuning of VdW magnets toward new ground states. Chromium trihalides provided the first such example with a change of interlayer magnetic coupling emerging upon exfoliation. Here, we take a different approach to engineer previously unknown ground states, not by exfoliation, but by tuning the spin-orbit coupling (SOC) of the nonmagnetic ligand atoms (Cl, Br, I). We synthesize a three-halide series, CrCl<sub>3 - <i>x</i> - <i>y</i></sub> Br <i><sub>x</sub></i> I <i><sub>y</sub></i> , and map their magnetic properties as a function of Cl, Br, and I content. The resulting triangular phase diagrams unveil a frustrated regime near CrCl<sub>3</sub>. First-principles calculations confirm that the frustration is driven by a competition between the chromium and halide SOCs. Furthermore, we reveal a field-induced change of interlayer coupling in the bulk of CrCl<sub>3 - <i>x</i> - <i>y</i></sub> Br <i><sub>x</sub></i> I <i><sub>y</sub></i> crystals at the same field as in the exfoliation experiments.