Effect of Joule-Heating Annealing on Giant Magnetoimpedance of Co64Fe4Ni2B19-xSi8Cr3Alx (x = 0, 1 and 2) Melt-Spun Ribbons

In this work, we have studied the influence of dc joule-heating thermal processing on the structure, magnetoimpedance (MI) and thermal properties of Co64Fe4Ni2B19-xSi8Cr3Alx (x = 0, 1, and 2) rapidly solidified melt-spun ribbons. The nanocrystallization process was carried out by the current annealing of as-spun samples at various current densities. As-spun and joule-heated samples were studied by X-ray diffraction (XRD), differential scanning calorimeter (DSC), and magnetoimpedance (MI) measurements. DSC results revealed that by the replacement of B by Al the first and second crystallization peaks are overlapped with each other and the initial nanocrystallization temperature is decreased with the increase in Al content of the alloy. Also it was shown that the replacement of B by Al atoms can improve soft magnetic properties confirmed by magnetoimpedance ratio (MIR%) results for the amorphous joule-heated ribbons. Furthermore, increase in dc joule current density increases the MI ratio first, however; after formation of crystalline phases, it decreases.