Intrinsic Topological Weyl Phase Transition Induced by a Magnetostructural Transformation in a Kagome Magnet

TL;DR

This study demonstrates an intrinsic topological Weyl phase transition in a kagome magnet induced by a magnetostructural change near room temperature, revealing new topological states and spintronic potential.

Contribution

It reports the first observation of a Weyl phase transition driven by a magnetostructural transformation in Mn$_3$Ga near room temperature.

Findings

Transition from type-II to a distinct Weyl state occurs near room temperature.

Significant changes in anomalous Hall and topological Hall effects are observed.

Magnetostructural transition involves a change to a monoclinic structure with canted antiferromagnetic order.

Abstract

Topological phase transitions provide a unique window into the interplay between structure, magnetism, and Weyl physics in magnetic Weyl semimetals. However, realizing an intrinsic Weyl phase transition between two distinct Weyl states near room temperature remains challenging. Here, we demonstrate that a magnetostructural transition effectively induces such a transition in the kagome magnet Mn$_3$Ga. High-resolution neutron diffraction, magnetization characterizations and first-principles calculations reveal that Mn$_3$Ga undergoes a chiral antiferromagnetic transition below 485 K, followed by a magnetostructural transition to a monoclinic structure with highly canted antiferromagnetic order near room temperature. These cooperative changes in lattice and magnetic symmetries reorganize Weyl nodes, driving a transition from a primary type-II Weyl state to a distinct Weyl state, accompanied by dramatic variations in the anomalous Hall effect and appearance of topological Hall effect. Our findings open a new pathway for discovering novel topological Weyl states and potential spintronic applications.