Thermal, magnetic, and magnetomechanical properties of Metglas 2605 S2 and S3

Abstract

The magnetomechanical coupling factor K33 (as a function of annealing temperature Ta and bias field) and crystallization characteristics have been measured for two metallic glasses, Metglas 2605 S2 and S3. In the S3 alloy, K33 increases with increasing Ta, with a maximum of 0.85 between 385 and 400 °C, and declines sharply above 400 °C. S2, on the other hand, has a broad plateau in K33 between 400 and 430 °C (the upper limit of Ta in the experiment), with a value of K33 of 0.93. DSC curves show that both glasses crystallize in two stages with activation energies of 4.81 and 4.35 eV for S2 and S3. The Curie temperature TC was measured as a function of annealing time and temperature for the S2 composition. Plots of TC versus Ta show a straight line region, corresponding to structural relaxation, followed by a region of increasing slope, due to incipient crystallization. Samples of K33 which were magnetically annealed to produce high K33 and subsequently nonmagnetically annealed at 250 or 300 °C showed a decrease of K33. Following an additional magnetic anneal at 415 °C, the value of K33 was restored to its original value. It is clear from these results that loss of transducer function is due, not to crystallization effects, but to loss of anisotropy.