# Imaging stress and magnetism at high pressures using a nanoscale quantum sensor

## TL;DR

This paper presents a nanoscale quantum sensor integrated into diamond anvils for high-resolution imaging of stress and magnetism at high pressures, enabling new insights into phase transitions and material properties.

## Contribution

It introduces a novel NV-center-based sensing platform embedded in diamond anvils for in situ high-pressure imaging of stress and magnetic fields.

## Key findings

- Achieved diffraction-limited imaging (~600 nm) of stress and magnetism up to 30 GPa.
- Quantified all six stress components with accuracy <0.01 GPa.
- Demonstrated vector magnetic field imaging and phase transition detection in iron and gadolinium.

## Abstract

Pressure alters the physical, chemical and electronic properties of matter. The development of the diamond anvil cell (DAC) enables tabletop experiments to investigate a diverse landscape of high-pressure phenomena ranging from the properties of planetary interiors to transitions between quantum mechanical phases. In this work, we introduce and utilize a novel nanoscale sensing platform, which integrates nitrogen-vacancy (NV) color centers directly into the culet (tip) of diamond anvils. We demonstrate the versatility of this platform by performing diffraction-limited imaging (~600 nm) of both stress fields and magnetism, up to pressures ~30 GPa and for temperatures ranging from 25-340 K. For the former, we quantify all six (normal and shear) stress components with accuracy $<0.01$ GPa, offering unique new capabilities for characterizing the strength and effective viscosity of solids and fluids under pressure. For the latter, we demonstrate vector magnetic field imaging with dipole accuracy $<10^{-11}$ emu, enabling us to measure the pressure-driven $\alpha\leftrightarrow\epsilon$ phase transition in iron as well as the complex pressure-temperature phase diagram of gadolinium. In addition to DC vector magnetometry, we highlight a complementary NV-sensing modality using T1 noise spectroscopy; crucially, this demonstrates our ability to characterize phase transitions even in the absence of static magnetic signatures. By integrating an atomic-scale sensor directly into DACs, our platform enables the in situ imaging of elastic, electric and magnetic phenomena at high pressures.