Electro-optical timer for improved anisotropy magnetometer

The torsion-oscillator magnetometer is a simple magneto-mechanical instrument for determining the magnetization 4πM and magnetocrystalline anisotropy field H_a of nonconducting materials. To extend the range of applicability, an electrooptical chopper and pulse counter have been incorporated for the accurate and rapid measurement of oscillation periods less than 100 ms. With these improvements, accurate values of 4πM and H _a were measured for highly anisotropic oriented ceramic magnets of the M-type magnetoplumbites that require applied fields above 10 kOe. The anisotropy magnetometer has been improved in two important ways: (i) the range of applicability has been extended to much shorter periods, thereby permitting the measurement of very high anisotropy materials that include c-axis aligned M-type hexagonal ferrites, and (ii) the improved convenience and precision have all but eliminated timer and operator errors that plagued the original version of the instrument, which was operated manually