Ultimate tunability of ferromagnetic anisotropy in chromium mixed halides

In recent years, chromium iodide, bromide, and chloride have received attention due to exhibiting ferromagnetic ordering in 2D which is ideal for ultrathin magneto-optical devices. Also, it has been demonstrated that by alloying the halides, the magnetic easy axis can be tuned. Here, we show the ultimate case of such alloying, by presenting a new material CrClBrI where all three halides are mixed in one composition. The crystals of CrClBrI are thin and exfoliate. We present a phase diagram of all compositions of mixed halides and demonstrate how the critical temperature, Weiss constant, and magnetic anisotropy are continuously tuned across the series.