Polymorphic spin ordering in a single-crystalline cobalt-doped Fe3GaTe2

TL;DR

This study reveals polymorphic spin ordering in cobalt-doped Fe3GaTe2, where multiple magnetic states coexist without structural changes, controlled by Co doping and temperature, supported by experimental and theoretical analyses.

Contribution

It demonstrates the emergence of three distinct magnetic states in a single crystal without structural phase transitions, driven by Co doping.

Findings

Three magnetic phases: ferromagnetic, collinear antiferromagnetic, non-collinear antiferromagnetic.

Multiple critical temperatures: 210 K, 110 K, and 30 K.

Supported by magnetic microscopy, first-principles calculations, and spectroscopy.

Abstract

A single crystalline system typically stabilizes a unique state for spin ordering below a critical temperature. Certain materials exhibit multiple magnetic states, driven by structural phase transitions under varying thermodynamic conditions. Recently, van der Waals magnets have demonstrated subtle interlayer exchange interactions, offering a promising approach to electrically control spin states without structural transformation. Here, we report the emergence of three distinct magnetic states, ferromagnetic ordering and both collinear and non-collinear antiferromagnetic orderings, in a layered single crystalline magnet, cobalt-doped Fe3GaTe2 ((Co, Fe)3GaTe2). These three magnetic phases occur without structural phase transitions, a phenomenon we designate as polymorphic spin ordering in the material. The introduction of 16% Co-doping in Fe3GaTe2 modulates the interlayer magnetic interaction, enabling multiple spin orderings within the same lattice system with three critical temperatures: a Curie temperature for a ferromagnetic state (Tc=210 K) and two Neel temperatures for the collinear (TN1=110 K) and non-collinear (TN2=30 K) antiferromagnetic states. Our findings are supported by magnetic force microscopy, first-principles calculations, and circular dichroism angular photoemission spectroscopy, which reveals varying spin ordering and changes in the topological band structure and Berry curvature at different temperatures within the single-crystalline (Co, Fe)3GaTe2.