High-temperature giant magnetoimpedance in Fe-based nanocrystalline alloy

Giant magnetoimpedance (GMI) was investigated from room temperature up to 8 23 K in an Fe-based nanocrystalline Fe73.0Cu1.0Nb2.5V1.0Si13.5B9.0 ribbon. With an increment of the measuring temperature (T), GMI shows notable enhan cement followed by a declining dependence, yielding a maximum value around 603 K where the relative GMI is nearly four times that at room temperature. The field at the peak of the GMI vs H-dc curve decreases monotonically wit h T, but around T=603 K there superimposes a trough-shaped variation. The t hermal evolution of the soft magnetic property and magnetic anisotropy is s uggested to be responsible for the high-temperature GMI features. Discussio n on the intergrain exchange magnetic coupling through the amorphous bounda ries in the two-phase Fe-based nanocrystalline alloy is also given. (C) 200 0 American Institute of Physics. [S0021-8979(00)75308-4].