Antiferromagnetic α-MnTe: Molten-Salt-Assisted Chemical Vapor Deposition Growth and Magneto-Transport Properties

Abstract

Antiferromagnetic (AF) materials are attracting increasing interest for research in magnetic physics and spintronics. Here, we report a controllable synthesis of room-temperature AF α-MnTe nanocrystals (Néel temperature ∼307 K) via the molten-salt-assisted chemical vapor deposition method. The growth kinetics are investigated regarding the dependence of flake dimension and macroscopic shape on growth time and temperature. The high crystalline quality and atomic structure are confirmed by various crystallographic characterization means. Cryogenic magneto-transport measurements reveal anisotropic magnetoresistance (MR) response and complicated dependence of MR on temperature, owing to the subtle competition among multiple scattering mechanisms of thermally excited magnetic disorders (magnon drag), magnetic transition, and thermally populated lattice phonons. Overall positive MR behavior with two transitions in magnitude is observed when out-of-plane external magnetic field (B) is applied, while a transition from negative to positive MR response is recorded when in-plane B is applied. The rich magnetic transport properties render α-MnTe a promising material for exploiting functional components in magnetic devices.

Recent Developments in Chemical Vapor Deposition of 2D Magnetic Transition Metal Chalcogenides

“…(i) Evolution of the products of CVD synthesized MnTe nanosheets and (j) their transition from antiferromagnetism to paramagnetism characterized by magnetoresistance. Reproduced with permission from ref . Copyright 2022 American Chemical Society.…”

“…In the case of manganese, manganese chalcogenides (M m X n ) are not layered materials. However, using mica as the growth substrate, ultrathin M m X n can be prepared, including MnS, MnSe, and MnTe (Figure i). ,, This makes it possible to study their transport properties on single-crystalline nanomaterials. In a recent work published by Li et al, the transition from antiferromagnetism to paramagnetism of CVD synthesized α-MnTe nanosheets were characterized by magnetotransport, and the competition between thermally excited magnons and lattice phonons was observed (Figure j).…”

“…However, using mica as the growth substrate, ultrathin M m X n can be prepared, including MnS, MnSe, and MnTe (Figure i). ,, This makes it possible to study their transport properties on single-crystalline nanomaterials. In a recent work published by Li et al, the transition from antiferromagnetism to paramagnetism of CVD synthesized α-MnTe nanosheets were characterized by magnetotransport, and the competition between thermally excited magnons and lattice phonons was observed (Figure j). All the above demonstrates that CVD is a powerful technique to prepare 2D magnetic TMCs, and more fascinating phenomena in other compounds and their heterostructures are awaiting exploration.…”

“…Compared with other synthesis methods, attributes of CVD, such as large scale, high quality, and great tunability, render CVD approaches to gradually become the dominant method for preparing various kinds of 2D materials. − Compared with other 2D materials, TMCs with the general formula of M a X b (where M refers to a transition metal and X represents a chalcogen) exhibit rich structures and versatile properties, ,,,− which thus provides an ideal platform for exploring 2D magnetism. Up until now, remarkable progress has been achieved with the study on 2D magnetic TMCs, − especially the chromium (Cr), iron (Fe), vanadium (V), and manganese (Mn)-based chalcogenides (Cr m X n , Fe m X n , V m X n , and Mn m X n ), where ultrathin flakes with controllable phase and thickness have been successfully synthesized and the associated magnetic properties have been systematically studied. For instance, researchers have found out that by controlling the growth temperature, 2D FeTe in different phases (i.e., tetragonal vs hexagonal) can be selectively prepared, demonstrating distinct magnet responses (i.e., antiferromagnetism vs ferromagnetism) .…”

Atomic imaging and thermally induced dynamic structural evolution of two-dimensional non-layered Cr2S3

“…19,20 Salt is considered to have two primary effects: lowering the melting point of the metal precursor and increasing the vapor pressure of the target metal. 21,22 The second effect lowers the activation energy of particular planes and induces the distortion effect, which prevents isotropic growth and promotes lateral growth. 23 He et al obtained unit-cell-thick non-layered Cr 2 S 3 nanosheets by a NaClassisted CVD method using a CrCl 3 metal precursor.…”