Substances exhibit many novel properties under high pressure, for example, pressure can induce insulator-metal or even superconductor transition. However, in-situ magnetic measurement has always been a difficult problem in high pressure research, limiting the study of the Meissner effect of superconductors and the magnetic phase transition behavior of magnetic materials at high pressures.

A new high-pressure in-situ magnetic detection method has been developed by a collaborative research group from the Hefei Institutes of Physical Science (HFIPS), the University of Science and Technology of China of the Chinese Academy of Sciences, and Sichuan University, paving the way to use divacancy in quantum technologies as pressure sensing and magnetic detection at high-pressures.

Results were published on Nano Letters.

"For the first time, we have achieved coherent control and high-pressure magnetic detection of divacancy defects in SiC spin quantum states under high pressure," said LIU Xiaodi, co-leader of the project and associate professor at HFIPS.

In this study, with spin quantum sensing technology of silicon carbide divacancy defects, diamond anvil cell technology, and optically detected magnetic resonance (ODMR) technology, the researchers realized coherent control of the quantum states of silicon carbide divacancy defects under high pressure and magnetic detection based on the spin of silicon carbide divacancy defects.

The divacancy defect spin in silicon carbide (SiC) is highly responsive to external pressure and magnetic field, and these responses can be measured by highly sensitive ODMR spectra, thus characterizing the pressure and magnetic state of the sample under high pressure.

The researchers then systematically studied the optical and spin properties of divacancy defects in SiC under high pressure. Results show that the pressure sensing sensitivity of double vacancy PL5 defect is 0.28 MPa/Hz^-1/2.

Based on the coherent control of spin quantum states of divacancy in SiC under high pressure, the ferromagneto-paramagnetic phase transition of magnetic Nd₂Fe₁₄B was detected under high pressure.

This work was supported by the National Natural Science Foundation of China, the Ministry of Science and Technology of China, the Youth Innovation Promotion Association of CAS, etc.

The optical and spin properties of silicon carbide divacancy defects under high pressure were studied by using diamond anvil cell. (Image by LIU Lin) 

Detection of pressure-induced magnetic phase transition of a Nd₂Fe₁₄B magnet using PL6 defects. (Image by LIU Lin)