Fig. 2: Properties of an NV-MED sensing, visualising, and memorising a magnetic field.

a EL intensity of NV-MED under different applied magnetic fields from 60 to 210 mT. b NV-MED under different magnetic fields, i.e. 210, 110 and 70 mT (scale bars: 1 mm). c Plots of the change in EL intensity of an NV-MED as a function of magnetic field. d Variation in EL intensity of an NV-MED in writing and erasing with different magnetic fields. A scheme of magnetic field programming for writing and erasing the EL in inset. e Time-dependent retention of EL intensity arising from an NV-MED with different magnetic fields. f Write–erase endurance cycle of EL intensity changes of an NV-MED. The inset shows the EL intensity change in one cycle and scheme of four magnetic field programmes for the endurance cycle. g NV-MED demonstrating the EL-based magnetic field programme/erase process (scale bars: 4 mm). h NV-MED with different magnetic-field shapes showing the direct visualisation of the magnetic field in EL with the device (scale bars: 5 mm). i Endurance cycle test of EL intensity under 210 mT magnetic field.