Bilayer orthogonal ferromagnetism in CrTe$_2$-based van der Waals system

TL;DR

This study uncovers a novel orthogonal-ferromagnetic phase in CrTe2-based van der Waals systems, revealing abrupt spin transitions and offering new insights for spintronic device development.

Contribution

It identifies a previously overlooked magnetic phase with alternating in-plane and out-of-plane ferromagnetic layers, differing from known crossed magnetism, and clarifies the nature of spin reorientation in CrTe2 compounds.

Findings

Discovery of orthogonal-ferromagnetism in CrTe2-based systems

Evidence of abrupt spin-flop transitions

Potential for enhanced spintronic applications

Abstract

Systems with pronounced spin anisotropy play a pivotal role in advancing magnetization switching and spin-wave generation mechanisms, which are fundamental for spintronic technologies. Quasi-van der Waals ferromagnets, particularly Cr$_{1+\delta}$Te$_2$ compounds, represent seminal materials in this field, renowned for their delicate balance between frustrated layered geometries and magnetism. Despite extensive investigation, the precise nature of their magnetic ground state, typically described as a canted ferromagnet, remains contested, as does the mechanism governing spin reorientation under external magnetic fields and varying temperatures. In this work, we leverage a multimodal approach, integrating complementary techniques, to reveal that Cr$_{1+\delta}$Te$_2$ ($\delta = 0.25 - 0.50$) hosts a previously overlooked magnetic phase, which we term orthogonal-ferromagnetism. This single phase consists of alternating atomically sharp single layers of in-plane and out-of-plane ferromagnetic blocks, coupled via exchange interactions and as such, it differs significantly from crossed magnetism, which can be achieved exclusively by stacking multiple heterostructural elements together. Contrary to earlier reports suggesting a gradual spin reorientation in CrTe$_2$-based systems, we present definitive evidence of abrupt spin-flop-like transitions. This discovery, likely due to the improved crystallinity and lower defect density in our samples, repositions Cr$_{1+\delta}$Te$_2$ compounds as promising candidates for spintronic and orbitronic applications, opening new pathways for device engineering.