Investigation of temperature dependence of magnetic properties of Cr$_2$O$_3$ thin film structure using a magnetic field imaging technique based on Nitrogen-Vacancy centres in diamond crystal

TL;DR

This study employs Nitrogen-Vacancy centre-based magnetometry to investigate the temperature-dependent magnetic phase transition in Cr₂O₃ thin films, revealing unexpected diamagnetic-like behavior below the Néel temperature with high spatial resolution.

Contribution

It introduces a novel application of NV centre magnetometry for detailed, microscopic analysis of magnetic phase transitions in thin films, demonstrating its effectiveness compared to traditional methods.

Findings

Detected magnetic phase transition at Née temperature.

Observed diamagnetic-like behavior below Née temperature.

Validated the technique's capability for spatial magnetic field mapping.

Abstract

This work presents a magnetic field imaging method based on color centres in diamond crystal applied to thin film structure. To demonstrate the capacity of our device we have used it for characterization of magnetic properties in microscopic scale of Cr$_2$O$_3$ thin film structure above and below N\'eel temperature. The obtained measurement results clearly identify the detection of the magnetic phase transition of Cr$_2$O$_3$ thin film with an unexpected diamagnetic like behaviour at 19$^{\circ}$C (below the N\'eel temperature of Cr$_2$O$_3$). To have better insights in the magnetic fields created by the thin films we present simulations of the magnetic fields near the thin film surface. We also analysed the optically detected magnetic resonance (ODMR) profiles to be sure that the measured property is related only to the shift of the optically detected magnetic resonance. We demonstrate how Nitrogen-Vacancy centre based magnetometry can deliver a convenient platform for research of phase transition dynamics and spatial magnetic field distributions of thin films, that can rival other widely used measurement techniques.