Temperature-variable apparatus for measuring Barnett field

We have developed experimental equipment for observing the Barnett effect, in which mechanical rotation magnetizes an object, at low temperatures. A sample in a rotor is rotated bidirectionally using a temperature-controlled high-pressure gas. The stray field generated from the sample due to the Barnett effect was detected using a fluxgate magnetic sensor with a sensitivity on the order of several picoteslas, even at low temperatures. By replacing the rotor with a solenoid coil, the magnetic susceptibility of the sample was estimated from the stray field to be of the same order of magnitude as that due to the Barnett effect. The Barnett field was estimated using the dipole model. To assess the performance of the setup at low temperatures, measurements were performed on commercial magnetite (Fe3O4) nanogranules. We confirmed the accordance of the g' factor between the experimental results using the present setup and those of our previous study performed at room temperature.

Automated summary

We have developed experimental equipment to observe the Barnett effect at low temperatures. By rotating the sample bidirectionally using a temperature-controlled high-pressure gas, we detected the stray field generated by the Barnett effect using a fluxgate magnetic sensor. The magnetic susceptibility of the sample was estimated to be of the same order of magnitude as that due to the Barnett effect, by replacing the rotor with a solenoid coil. Measurements on commercial magnetite nanogranules confirmed the accordance of the g' factor between the experimental results using the present setup and those of our previous study performed at room temperature.