In contrast to whole blood, in plasma, the decrease in the T 1 relaxation time of protons was observed with the variation of the storage field from 10 µT to 510 µT (Fig. ). This complicated dependence of the relaxation times on the storage field can be attributed to a sample heating in the proximity of an operating atomic magnetometer. Indeed, in our magnetic-field profile measurements, the storage field was increased step by step without changing the sample. Even though the T 2 relaxation time (extracted from the linewidth) was measured at the same detection field, we observed its decrease in the subsequent experiments (Fig. ). This additionally confirms the effect of temperature on the measured relaxation times. When the sample temperature was measured by thermocouple as a function of acquisition time (time the sample spent near the atomic magnetometers), we observed that it could exceed 40 • C, as shown in Fig. . Therefore, the repeated measurements might cause an increase in the temperature of the sample over time and could cause faster relaxation . To overcome this limitation, active cooling or/and temperature stabilization can be implemented in the setup to maintain temperature stability . It should also be noted that the T 2 values are consistently lower than the T 1 values, which resulted from the additional contribution of low-frequency fluctuations such as slow molecular rotation, chemical exchange, and diffusion to the transverse relaxation .