GIANT MAGNETOIMPEDANCE EFFECTS IN THE SOFT FERROMAGNET FE73.5CUNB3SI13.5B9

The components of the resistance R and the reactance X of the complex impedance Z = R + iX, as well as the relative effective permeability m u', for as-quenched and nanocrystalline Fe73.5CuNb3Si3.5B9 ribbons hav e been studied as functions of drive current frequency (1 kHz to 13 MH z) and longitudinal magnetic field (-75 to 75 Oe). For as-quenched sam ples, a mostly resistive feature was found over the whole frequency ra nge. The magnetoimpedance effect was more sensitive for nanocrystallin e samples: at 3 MHz, R and X, respectively, increased 10% and 16% at a longitudinal field of 4 Oe, or decreased 47% and 33% at a 75 Oe field . The magnetic responses of both R and X for nanocrystalline samples s howed a maximum at about 4 Oe, whereas there was no maximum for as-que nched samples. The field dependence of effective permeability for nano crystalline samples showed a sharp reduction at about 4 Oe; which is b elieved to be the anisotropy field.