Electrical Interrogation of Thickness‐Dependent Multiferroic Phase Transitions in the 2D Antiferromagnetic Semiconductor NiI2

Abstract

Abstract2D magnetic materials hold promise for quantum and spintronic applications. 2D antiferromagnetic materials are of particular interest due to their relative insensitivity to external magnetic fields and higher switching speeds compared to 2D ferromagnets. However, their lack of macroscopic magnetization impedes detection and control of antiferromagnetic order, thus motivating magneto‐electrical measurements for these purposes. Additionally, many 2D magnetic materials are ambient‐reactive and electrically insulating or highly resistive below their magnetic ordering temperatures, which imposes severe constraints on electronic device fabrication and characterization. Herein, these issues are overcome via a fabrication protocol that achieves electrically conductive devices from the ambient‐reactive 2D antiferromagnetic semiconductor NiI2. The resulting gate‐tunable transistors show band‐like electronic transport below the antiferromagnetic and multiferroic transition temperatures of NiI2, revealing a Hall mobility of 15 cm2 V−1 s−1 at 1.7 K. These devices also allow direct electrical probing of the thickness‐dependent multiferroic phase transition temperature of NiI2 from 59 K (bulk) to 28 K (monolayer).