  Diamond samples of defects with negative charged nitrogen-vacancy (NV)
centers are promising solid state spin sensors suitable for quantum information
processing, high sensitive measurements of magnetic, electric and thermal
fields in nanoscale. The diamond defect with a NV center is unique for its
robust temperature-dependent zero field splitting Dgs of the triplet ground
state. This property enables optical readout of electron spin states through
manipulation of the ground triplet state using microwave resonance with Dgs
from 100 K to about 600 K. Thus, prohibiting Dgs from unwanted external thermal
disturbances is crucial for an accurate measurement using diamond NV sensors.
Our observation demonstrates the existence of a prominent microwave heating
effect on the diamond samples of NV centers. The effect is inevitable to shift
Dgs and cause measurement errors. The temperature increment caused by the
effect monotonically depends on the power and the duration of microwave
irradiation. The effect is obvious with the microwave irradiation in the
continuous mode and some pulse sequence modes, but is neglectable for the
quantum lock-in XY8-N method.
