Studying the magnetism of 2D magnet CrTe₂and tuning its magnetic properties via Nb doping

Two-dimensional (2D) ferromagnetic materials opened many opportunities for the fundamental exploration of magnetism and promise for high-density, miniaturized spintronic devices. Recently, CrTe₂ has gained significant attention due to several compelling features, such as the high Curie temperature (T_c) [1]. Here, we grow mm-sized bulk CrTe₂ crystals using indirect synthesis methods by removing K from parent KCrTe₂ crystals with the aid of I₂ in Acetonitrile. The high crystal quality is verified through a combination of characterization techniques, including X-ray diffraction, scanning electron microscopy, transmission electron microscope, and energy-dispersive X-ray spectroscopy. The bulk magnetic properties were measured using a vibrating-sample magnetometer and ferromagnetic resonance (FMR) spectroscopy. The grown CrTe₂ crystals process ferromagnetism with T_c of ~350 K and a saturation magnetization at ~ 140 mT. To tune the magnetic properties of CrTe₂, we doped it with Nb as Cr_0.8Nb_0.2Te₂. We found that Cr_0.8Nb_0.2Te₂ also exhibits ferromagnetism with T_c of ~295 K and saturation magnetization at ~140 mT. FMR measurements on Cr_0.8Nb_0.2Te₂ microcrystal reveal low FMR frequencies (down to ~ 1 GHz) and Gilbert damping constant a of 0.08 in comparison to the undoped CrTe₂ with FMR frequency above 4 GHz and a damping constant a of 0.05. These changes can be explained by the modification of effective magnetic anisotropy. [1] X. Zhang, et al., Nat Comm.12, 2492 (2021).