# Spin chirality fluctuation in two-dimensional ferromagnets with perpendicular anisotropy

## TL;DR

This study provides direct evidence of universal spin chirality fluctuations in two-dimensional ferromagnets with perpendicular anisotropy, revealed through topological Hall effect measurements above transition temperatures.

## Contribution

It demonstrates that spin chirality fluctuation is a universal phenomenon in 2D Ising ferromagnets, supported by experimental data and Monte-Carlo simulations.

## Key findings

- Spin chirality fluctuation observed above transition temperatures.
- The THE signal depends on temperature, magnetic field, thickness, and carrier type.
- Monte-Carlo simulations confirm the universality of the phenomenon.

## Abstract

Non-coplanar spin textures with scalar spin chirality can generate effective magnetic field that deflects the motion of charge carriers, resulting in topological Hall effect (THE), a powerful probe of the ground state and low-energy excitations of correlated systems. However, spin chirality fluctuation in two-dimensional ferromagnets with perpendicular anisotropy has not been considered in prior studies. Herein, we report direct evidence of universal spin chirality fluctuation by probing the THE above the transition temperatures in two different ferromagnetic ultra-thin films, SrRuO$_3$ and V doped Sb$_2$Te$_3$. The temperature, magnetic field, thickness, and carrier type dependences of the THE signal, along with our Monte-Carlo simulations, unambiguously demonstrate that the spin chirality fluctuation is a universal phenomenon in two-dimensional Ising ferromagnets. Our discovery opens a new paradigm of exploring the spin chirality with topological Hall transport in two-dimensional magnets and beyond