Influence of dc Joule Annealing on Magnetoimpedance of CuBe/CoNiP Composite Wires

摘要

In this paper, the influence of dc Joule annealing on giant magnetoimpedance (GMI) effect for composite wires by electroless depositing [1] 12μm thickness CoNiP layer on CuBe wires with 150μm in diameter is presented. Successive thermal treatments by dc Joule annealing with current density ranging from 1.13 to 2.83×10{sup}8A/m{sup}2 are applied to the composite wires with 5cm in length for a constant annealing time of 10min. MI measurements are carried out using an impedance analyzer (HP4294A), the rms value of the ac driving current was kept constant at 5mA. The relative change of the GMI ratios were defined as △F/F(%)=(F(H)-F(H{sub}(max)))/F(H{sub}(max)) (1) where F can be regarded as impedance Z, resistance R and reactance X, H and H{sub}(max) are the arbitrary and maximum intensity of external magnetic field generated by a Helmholtz coil, respectively. The H{sub}(max) used for the measurements is 60Oe.