Dynamical variations in the local magnetic structure of FeGe, a transition metal that can support interesting states of magnetism, have been studied via the magnetic dependent optical signal from a single NV-Center placed on the surface.
Thermally driven magnetic domain dynamics were observed using magnetic force microscopy (MFM), including continuous domain structure changes and also more abrupt jump-like behavior. However, in order to verify that the interesting domain dynamics are not due to the magnetic form of measurement, the researchers used a non-evasive form of measurement using the NV-Center in diamond. This measurement was carried out using a hand-built confocal microscope along with a Montana Instruments closed-cycle cryostat. The sample was placed on a coplanar waveguide (CPW) to provide resonant microwave for EPR.
Because the optical signal is strongly dependent on the local magnetic field magnitude the NV-Center has been used recently as a very sensitive high-spatial resolution magnetometer in many scenarios. In this case the optically detected magnetic resonance signal splitting, witch is dependent on the magnitude of the local magnetic field provided by the local magnetic domains were monitored while the temperature of the material was adjusted from 300K-168K.
Figure 1: A schematic of the experimental situation with the NV placed on the bulk FeGe, and to the right is a ODMR signal splitting as a result of the higher magnetic order domain formation at lower temperatures, which leads to an increased local magnetic field.
Figure 2: A similar temperature dependency except that instead of a smooth and monotonic increase in the splitting, abrupt breakdowns in the magnetic domains are seen due to jump-like stochastically based anti-ferromagnetic behavior. This is also seen and confirmed in the MFM data.
Observation of local magnetization dynamics in the helimagnet FeGe, arXiv:1503.06622
This work was performed using a Montana Instruments Cryostation. This article should not be considered an endorsement of any product.