We have developed a compact low-Tc three axis superconducting quantum inter
ference device magnetometer (SQUID magnetometer) for geophysical applicatio
ns at low frequency from de up to 1 kHz, such as for searching for magnetiz
ed metals buried under the ground or moving magnetized objects, and for mea
surements of the geomagnetic fields, Relaxation oscillation SQUIDs (ROSs) w
hich have larger voltage outputs compared to that of standard SQUIDs have b
een used so that larger dynamic performance is obtained for stable operatio
n in the field.