Giant plateau-like topological Hall effect controlled by tailoring the magnetic exchange stiffness in a kagome magnet

TL;DR

This study demonstrates how tailoring the magnetic exchange stiffness in a kagome magnet induces a giant plateau-like topological Hall effect, revealing new ways to control topological states in magnetic materials.

Contribution

It introduces a novel structural engineering approach by substituting Mn with Cr in TbMn6Sn6, leading to a symmetry reduction and a record-high topological Hall resistivity.

Findings

Induced a plateau-like topological Hall effect with resistivity of 19.1 ohm cm.

Observed magnetic domain transition near 1 T at 180 K.

Showed the importance of broken kagome symmetry in topological magnetism.

Abstract

The ferrimagnet TbMn6Sn6 has attracted vast attention, because its pristine Mn kagome lattice with strong spin-orbit coupling and out-of-plane Tb-Mn exchange supports quantum-limit Chern topological magnetism which can be described by the simple spinless Haldane model. We unveil herein that engineering the kagome lattice through partial substitution of Mn with nonmagnetic Cr induces a striking structural reorganization-Cr preferentially concentrates within a single Mn layer per unit cell, reducing the crystal symmetry from the D6h point group to the C2. This tailored structure configuration gives rise to a plateau-like topological Hall effect (THE), achieving a record-breaking resistivity of 19.1 ohm cm among bulk systems. Complementary magnetic force microscopy measurements unveil a magnetic domain transition near 1 T at 180 K, aligning with the field-dependent phase diagram of the THE. Our direct visualization of the magnetic domain structure underscores the critical role of broken kagome lattice symmetry in generating distinct exchange stiffness between the two Mn layers. These findings establish a new paradigm for exploring exotic states in kagome topological magnets and provide a proof-of-principle strategy for unraveling the interplay between magnetism and emergent topological properties in kagome systems.