NEW DESIGN OF SMALL-ANGLE MAGNETIZATION ROTATION DEVICE - EVALUATION OF SATURATION MAGNETOSTRICTION IN WIDE THIN RIBBONS

We present here a newly designed device allowing lambda(S) measurement s on ferromagnetic ribbons (width up to 30 mm, thickness approximate t o 20 mu m). It is based on the ''small-angle magnetization rotation'' method. Estimation of the ac drive field and its homogeneity into the material have been looked into. Calculations by finite elements method (MAXWELL 2D) are compared to H-coil measurements. Influence of de bia s field on transverse demagnetizing field has been taken into account. The aim of this work is to analyze, by lambda(S) measurements, the ev olution of composite structure (amorphous+crystalline) in accordance w ith annealing treatments between 450 and 600 degrees C of nanocrystall ine Finemet Fe73.5Si15.5B7CU1Nb3 ribbons. Results show that the value and the sign of the saturation magnetostriction lambda(S) are importan t because they are related to the magnetoelastic properties. Furthermo re, the observed magnetoelastic behavior (via variation of magnetizati on energy in accordance with external applied stress) is highly depend ent of the sign of lambda(S) even with a small value (approximate to 1 0(-7)). (C) 1997 American Institute of Physics.