# Magnetic measurements on micron-size samples under high pressure using designed NV centers

## TL;DR

This paper introduces an optical magnetometry method using NV centers in diamond anvils to measure magnetic properties of micron-sized samples under high pressure, providing a new link between microscopic and macroscopic magnetism.

## Contribution

It presents a novel approach for magnetic measurements under high pressure using NV centers, bridging the gap between microscopic and macroscopic magnetic property assessments.

## Key findings

- Observed the ferromagnetic collapse of iron at 30 GPa.
- Detected the superconducting transition of MgB2 at 7 GPa.
- Demonstrated the method's effectiveness at room and low temperatures.

## Abstract

Pressure is a unique tool to tune the interplay between structural, electronic and magnetic interactions. It leads to remarkable properties of materials such as recent temperature records in superconductivity. Advanced magnetic measurements under very high pressure in the Diamond Anvil Cell (DAC) use synchrotron approaches but these are lacking a formal link to the macroscopic magnetic properties. We report an alternative method consisting in optical magnetometry based on nitrogen-vacancy (NV) centers created at the surface of a diamond anvil. We illustrate the method by two measurements realized at room and low temperature respectively: the pressure evolution of the magnetization of an iron bead up to 30 GPa showing the iron ferromagnetic collapse and the detection of the superconducting transition of MgB2 at 7 GPa.