Temperature dependence of remagnetization process in bistable magnetic microwires

Magnetostrictive microwires exhibit bistable magnetic behavior characterized by square hysteresis loops, a consequence of the magnetization reversal by depinning of a single domain wall from the closure structure at one end of the wire. This bistable behavior spontaneously observed in magnetostrictive microwires has been previously thoroughly studied at room temperature. In the present work, the temperature dependence of the remagnetization process is investigated in magnetic microwires, a few micrometres in diameter, covered by glassy coating plus additional metallic coatings. The influence first of geometrical parameters as length and diameter is considered. Later on, an emphasis is placed on the influence of the Pyrex and additional sputtered and electroplated coatings on the temperature dependence of switching field. Bistability can be lost, depending on the character of the coating, when reducing the measuring temperature due to the thermally induced anisotropy arising from the differential thermal expansion coefficient of the composite wire. On the other hand, the temperature dependence of the switching field and its distribution function have been measured. It is shown that the switching field increases as temperature decreases, which is analyzed considering the thermally activated pinning mechanism and the magnetostrictive contribution.