A VERTICAL FORCE ALTERNATING-GRADIENT MAGNETOMETER

This paper describes a modification of the alternating-gradient magnetometer that is especially suitable for measurements from 77 to 900 K. The gradient of the alternating field, and the resulting force on the sample are made perpendicular to the magnetization of the sample and a cantilevered piezoelectric sensing element can then be located in a constant temperature environment so that the mechanical resonant frequency and gain of the magnetometer are not influenced by changes in sample temperature. The instrument has a sensitivity of 10-8 emu/(Hz)1/2 for measuring small or weakly magnetic samples, but can easily be adapted to measure relatively massive or strongly magnetic samples. Samples weighing more than 1 g and magnetic moments above 1 emu have been measured. These limits can generally be raised by using heavy piezoelectric elements and extension fibers.