CONTINUOUS DRIFT CORRECTION AND SEPARATE IDENTIFICATION OF FERRIMAGNETIC AND PARAMAGNETIC CONTRIBUTIONS IN THERMOMAGNETIC RUNS

The principle of a Curie balance was changed by using a sinusoidally c ycling applied magnetic field instead of a fixed applied field. This w as done with a horizontal translation type Curie balance. By cycling b etween field values B(min) and B(max), the output signal is amenable t o Fourier analysis. Partial Fourier analysis yields the fundamental ha rmonic and the second harmonic, termed SIG1 and SIG2 respectively. The se are related to the saturation magnetization (M(s)) by M(s) = {2 SIG 1-8 max)+B(min)/(B(max)-B(min))]}/[A''(B(max)-B(min))] and to the para magnetic susceptibility (chi(par)) by chi(par) = 8 SIG2/[A''(B(max)-B( min))2], whereby A'' is a.calibration constant. Through the Fourier an alysis continuous drift correction is achieved simultaneously. A perso nal computer takes care of field control, temperature control and data acquisition in real time mode, as well as processing the data, to yie ld SIG1 and SIG2. After the experiment, SIG1 and SIG2 are processed fu rther with a separate transversal filtering program that improves the signal-to-noise ratio. The working temperature range of the adapted ho rizontal translation type Curie balance is between room temperature an d 900-degrees-C. Its noise level corresponds to a magnetic moment of 2 x 10(-9) Am2, making it a very powerful tool for thermomagnetic analy sis of weakly magnetic material. Examples demonstrating this potential of the device are shown.