Fig. 3: Data for magnetic detection of magnetite.
a, b The Fluorescence (FL) imaging of NV centers in DACs exp1 and exp2, respectively. The fluorescence intensity tends to be lower beneath the Fe3O4 sample. The dashed blue square represents the area of Fe3O4 sample for eye guide. The filled black and white circle marks the NV centers below the side (NVo) and beneath (NVi) the Fe3O4 sample, respectively. c, d The ODMR spectra of NVo and NVi change with elevated pressures, respectively. The horizontal axis represents the frequency shift relevant to the center frequency of ms = ± 1 spin sublevels. The dashed black lines mark the resonant frequency of the NV centers far away from the sample, which is used to characterize the magnitude of the external magnetic field along NV axis (~130 G). The dashed blue lines and arrows mark the resonant frequency shift induced by the magnetic field from the sample. The dashed orange lines and arrows mark the spectrum broadening.
