Two-dimensional transition metal halide PdX 2 (X = F, Cl, Br, I): A promising candidate of bipolar magnetic semiconductors

Abstract

Two-dimensional (2D) nanomaterials with bipolar magnetism show great promise in spintronic applications. Manipulating carriers’ spin-polarized orientation in bipolar magnetic semiconductor (BMS) requires a gate voltage, but that is volatile. Recently, a new method has been proposed to solve the problem of volatility by introducing a ferroelectric gate with proper band alignment. In this paper, we predict that the PdX 2 (X = F, Cl, Br, I) monolayers are 2D ferromagnetic BMS with dynamic stability, thermal stability, and mechanical stability by first-principles calculations. The critical temperatures are higher than the boiling point of liquid nitrogen and the BMS characteristics are robust against external strains and electric fields for PdCl2 and PdBr2. Then, we manipulate the spin-polarization of PdCl2 and PdBr2 by introducing a ferroelectric gate to enable magnetic half-metal/semiconductor switching and spin-up/down polarization switching control. Two kinds of spin devices (multiferroic memory and spin filter) have been proposed to realize the spin-polarized directions of electrons. These results demonstrate that PdCl2 and PdBr2 with BMS characters can be widely used as a general material structure for spintronic devices.