SWEPT FREQUENCY PERMEAMETERS FOR MEASURING THE COMPLEX, OFF-DIAGONAL PERMEABILITY TENSOR COMPONENTS OF ANISOTROPIC, THIN MAGNETIC-FILMS

To better understand wave propagation through magnetic media we have m easured the high-frequency off-diagonal permeability tensor components of magnetic thin films using a thin-film permeameter. Although the of f-diagonal components are commonly considered to be of negligible valu e, for some materials they are substantial, of a magnitude comparable to that of the diagonal terms. Since the out-of-plane off-diagonal cou pling terms are primarily imaginary below resonance, and real above, t hey may introduce unexpected phase errors into the read/write process of magnetic recording and bulk material measurements and are therefore worthy of attention. The permeameters used to measured the off-diagon al terms are based upon the design of C. A. Grimes, P. L. Trouilloid, and R. M. Walser [IEEE Trans. Magn. MAG-24, 603 (1988)], which measure diagonal terms, but with different pickup coil and sample seat geomet ries. For z normal to the film, and with x and y defining, respectivel y, the hard and easy magnetization axes of the basal plane we measure mu(xy) and mu(xz). A microwave scattering parameter test set is used t o measure the scattering parameters of the jig from which the complex permeability is determined. The permeameters reported on here operate over the frequency range of approximately 10-600 MHz, and have a low l evel permeance detection limit of about 1 mum. Measurements of cosputt ered amorphous Co55Zr45 thin films show that the out-of-plane permeabi lity coupling term mu(xz) is a significant fraction of the basal plane hard axis permeability.