Computational method on magnetic properties of microwave ferrimagnets

Abstract

Central to microwave applications are iron garnet type materials involving rare earth elements. Most commonly they are based on Gd-Al substitutions-typically Y/sub 3-3x/Gd/sub 3x/Fe/sub 5-5y/Al/sub 5/O/sub 12/, offering wide temperature ranges of stable magnetic susceptibility, along with other desirable manufacturing characteristics. We were particularly interested in the coefficient of stability of magnetisation /spl alpha/=(4/spl pi/ M/sub max//sup S/-4/spl pi/ M/sub min//sup S/)/(4/spl pi/ M/sub 23/spl deg/C//sup S/) (/spl Delta/ T/sup -1/) and the temperature regions [T/sub 1/-T/sub 2/], /spl Delta/T=T/sub 2/-T/sub 1/ for which it is minimised. They determine their technological applications of the specific garnet materials; we established their location and /spl alpha//sub min/ for temperature ranges from 60/spl deg/ through 180/spl deg/C (in increments of 30/spl deg/C.) Extensive experimental studies of a variety of Gd-Al garnets demonstrate that all key magnetic parameters change in a liner manner as functions of Gd contents and Al contents. This suggests that the susceptibility curves (and computations) for new, yet to be synthesised Gd-Al garnets, can be generated through a suitable linear interpolation of the known compounds. We offer a computer-aided verification of this hypothesis followed by CAD of garnet type materials.<>