Study of the Solid Solubility Limit and Growth of Cd1–xMnxTe Multicomponent Single Crystals for Miniaturized Magneto-Optical Isolators

Cd1–xMnxTe (CMT) is a promising magneto-optical (MO) material for the visible to near-infrared region with a tunable bandgap via manganese (Mn) doping. Although CMT has been extensively studied, the solid solubility limit of Mn in CdTe (cadmium telluride) remains unclear, and the growth of high-Mn-content single crystals has not yet been reported in detail. In this work, the Mn solubility limit in CdTe was determined to be x = 0.71 by linear extrapolation of the lattice parameter based on X-ray diffraction (XRD) Rietveld refinement of polycrystalline powders with various Mn contents ranging from x = 0.1 to 0.8. CMT single crystals (x = 0.1, 0.2, 0.3, 0.5, and 0.7) were grown by referring to the solution limit using the vertical Bridgman method. With increasing Mn content, the absorption edge of CMT crystals exhibits a blue shift, and the optical bandgap of CMT increases from 1.585 to 2.082 eV. Due to its more suitable bandgap and larger Verdet constant compared to other Mn-doped contents, the optical transmittance, Mn ion valence state, elemental composition, and magnetic properties of the Cd0.7Mn0.3Te single crystal were studied and discussed. This study provides a reference for optimizing the Mn composition of CMT crystals for miniaturized MO isolators in the 700–1000 nm spectral region.