Diamond spies peek at magnetic secrets under Earth's core pressure ⚡ экспресс
Quantum sensing using nitrogen-vacancy centers in diamond to probe magnetic phase transitions, the Meissner effect, and stress distribution at extreme pressures has reached 140 GPa. To extend into the multi-megabar range needed for studying hydrogen-rich superconductors and mineral evolution in Earth's interior, shallow NV centers were created via ion implantation followed by HPHT annealing. This increased density, coherence, and reduced internal stress. NV magnetometry surpassed 240 GPa; the limit was the integrity of 50 µm diamond anvils. The Meissner effect and trapped flux were demonstrated at the superconducting transition in elemental titanium at a record pressure of 180 GPa. This result lays the foundation for high-pressure magnetometry in the search for quantum phenomena under previously inaccessible conditions.
In diamond, you can embed a “spy.” Simply replace a carbon atom with nitrogen—you get a defect that responds to magnetic fields and sends a light signal.
But ordinary spies can’t withstand colossal pressure. Scientists invented a tempering process: after nitrogen implantation, the diamond is annealed at extreme temperature and pressure. This strengthens the defects, letting them work even at 240 gigapascals—such pressure that diamond itself would flow if not prepared. Curiously, the spies sit right inside the diamond anvil that generates this pressure.
Previously, studying magnetic properties of materials under such pressure was impossible. Now, the spies will help reveal the secrets of superconductors that work without cooling. For instance, hydrogen at high pressure can become a perfect conductor, but its magnetic mysteries are yet to be spied on.
🎯 240 gigapascals is the pressure of a freight train balancing on a pinky fingernail. Even diamond needs tempering to survive such a squeeze.