High‐frequency permeability of laminated and unlaminated, narrow, thin‐film magnetic stripes (invited)

The permeability of the magnetic material in a thin‐film magnetic head is an important, but hard to characterize, parameter since the magnetic permeability depends on the head domain structure, the drive frequency, and the shape and size of the head. We have measured the high‐frequency permeability from 1 MHz to 300 MHz, hysteresis loops, and domain structure of unlaminated and multilayer magnetic thin‐films as a function of stripe width for arrays of long narrow stripes. Monolithic permalloy films and permalloy films laminated with SiO2 have been photolithographically patterned and ion‐milled to create 3 to 1000 μm wide rectangles, 1 cm long, with the hard axis oriented along the long axis of the rectangles. The high‐frequency permeability of each array of a given width is measured by the signal detected by a nonresonant butterfly‐coil pickup loop when the film is driven by a uniform radio‐frequency magnetic field generated by a strip‐line waveguide. The changes in domain pattern as the film structure an...