Tuning the Magnetic Properties of Cr_1-xNb_xTe₂ (x = 0 – 0.2) Crystals by Nb Doping

Recently, CrTe₂ has attracted significant attention in spintronics due to several compelling properties, such as the high Curie temperature (T_c) [1]. Here, we tune the magnetic properties by niobium (Nb) doping of mm to mm-sized CrTe₂ crystals. The high crystal quality of Cr_1-xNb_xTe₂ (x = 0 – 0.2) was confirmed by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. XRD confirms the dissolution of Nb into the CrNbTe₂ crystal structure, leading to a change in the lattice parameter, and causing a shift in XRD peak position. The bulk magnetic properties of Cr_1-xNb_xTe₂ crystals were measured using vibrating-sample magnetometer, superconducting quantum interference device magnetometer, and ferromagnetic resonance (FMR) spectroscopy. All doped crystals possess ferromagnetism with T_c of ~350 K for pristine crystals decreasing to ~295 K for Cr_0.8Nb_0.2Te₂ crystals. The saturation magnetization decreases from ~140 mT for x = 0 to ~38 mT for x = 0.2. FMR measurements on Cr_1-xNb_xTe₂ crystals reveal FMR frequencies in the range of 2 – 40 GHz and an increase of the Gilbert damping constant a from ~0.0665 for the pristine crystals to ~0.1232 for x = 0.2. These changes were explained by the modification of magnetic anisotropy and magnetic moment upon Nb doping, verified by Quantum ESPRESSO calculations [2]. [1] X. Zhang, et al., Nat. Comm. 12, 2492 (2021).