Ferromagnetic clusters in the monoclinic modification of TaFeTe2 layered van der Waals telluride

Abstract

Transition metal-based layered chalcogenides show intriguing magnetic properties, high tunability, and cleavability that allow fabrication of heterostructures with peculiar functional properties for designing spintronic devices, such as new types of low-power memory. TaFeTe₂ layered van der Waals telluride can be synthesized by chemical vapor transport reactions.The optimized synthesis conditions yield bulk single crystals of the new monoclinic polymorph with unit cell parameters of а ~ 7.3 Å, b ~ 6.1 Å, c ~ 8.2 Å, and β ~ 93 ° according to the indexing of electron diffraction patterns. Study of its crystal structure using high-resolution transmission electron microscopy confirms the monoclinic distortion and indicates the presence of hexagonal Ta honeycombs and Fe-Fe dumbbells. Band structure calculations show ferromagnetic ground state with magnetic moments of 1.5 μ_B on Fe atoms oriented perpendicular to the structural layers. Magnetic susceptibility and magnetization measurements confirm spin-glass state with T_f = 23 K and strong perpendicular magnetic anisotropy.