Nanoscale magnetic ordering dynamics in a high Curie temperature ferromagnet

TL;DR

This study uses advanced magnetometry techniques to investigate nanoscale magnetic behavior near the Curie temperature in a high-$T_c$ ferromagnet, revealing critical phenomena and universality classes.

Contribution

It demonstrates the application of scanning nitrogen-vacancy center magnetometry to probe static and dynamic critical behavior at the nanoscale in a high-$T_c$ ferromagnetic oxide.

Findings

Diverging correlation length near $T_c$ indicating 3D universality class.

Spin dynamics suggest XY universality class for the phase transition.

Static and dynamic critical behaviors captured at nanoscale.

Abstract

Thermally driven transitions between ferromagnetic and paramagnetic phases are characterized by critical behavior with divergent susceptibilities, long-range correlations, and spin dynamics that can span kHz to GHz scales as the material approaches the critical temperature $\mathrm{T_c}$, but it has proven technically challenging to probe the relevant length and time scales with most conventional measurement techniques. In this study, we employ scanning nitrogen-vacancy center based magnetometry and relaxometry to reveal the critical behavior of a high-$\mathrm{T_c}$ ferromagnetic oxide near its Curie temperature. Cluster analysis of the measured temperature-dependent nanoscale magnetic textures points to a 3D universality class with a correlation length that diverges near $\mathrm{T_c}$. Meanwhile, the temperature-dependent spin dynamics, measured through all optical relaxometry suggest that the phase transition is in the XY universality class. Our results capture both static and dynamic aspects of critical behavior, providing insights into universal properties that govern phase transitions in magnetic materials.