High-temperature ferromagnetism, large spin-valley polarization, and anomalous valley Hall effect in Janus GdISeH and GdITeH
Phys. Rev. B 113, 235409 – Published 3 June, 2026
DOI: https://doi.org/10.1103/lfpf-4nbm
Abstract
Two-dimensional Janus materials, characterized by their inherent structural asymmetry, provide an ideal platform for coupling magnetism with valleytronic properties. Herein, we propose two hydrogenated Janus monolayers, GdISeH and GdITeH, based on experimental layered , which leverage the strong spin-orbit coupling of gadolinium. Their structural, magnetic, electronic, and valleytronic properties are systematically investigated using first-principles calculations, Monte Carlo simulations, and Wannier function analysis. Both monolayers exhibit a ferromagnetic ground state with in-plane magnetic anisotropy (IMA) and high Curie temperatures of 216 K for GdISeH and 190 K for GdITeH. When magnetized out of plane, they exhibit substantial valley polarization (163 meV for GdISeH and 196 meV for GdITeH) along with prominent valley-contrasting Berry curvature, satisfying the key requirements for the anomalous valley Hall effect (AVHE). The electronic states are highly tunable: biaxial strain drives phase transitions among bipolar magnetic semiconductor (BMSC), bipolar magnetic semimetal (BMSM), and unipolar magnetic semiconductor (UMSC) phases, while carrier doping induces switching between BMSC and half-metal (HM) states. Notably, a low concentration of hole doping (below approximately 0.02 /f.u. for GdISeH and slightly above this for GdITeH) switches the magnetic anisotropy from IMA to perpendicular magnetic anisotropy, which is essential for stabilizing valley polarization and realizing the AVHE. The high-temperature ferromagnetism, large valley polarization, AVHE, as well as versatile BMSC, BMSM, UMSC, and HM characteristics with high spin polarization make Janus GdISeH and GdITeH monolayers promising candidates for spintronic and valleytronic applications.
