Improvement of the Ferromagnetic Resonance Linewidth of Single-Crystal ZnY (Ba2Zn2Fe12O22) by a New Growth Technique

Abstract

By using a new growth technique, ferromagnetic resonance linewidths as low as 8.0 Oe can be obtained in ZnY single crystals at room temperature and 9.0 kMc/sec. These crystals were grown in platinum crucibles from BaO–B₂O₃ melts. The melts were found to be less volatile and less viscous than NaFeO₂ melts. Annealing reduced the linewidth. The best conditions consisted of annealing raw crystals at 750°C in 1 atm of oxygen for 24 h. This treatment reduced the ferrous ion concentration to below the limit of detection, 0.01%, and is considered the major factor in linewidth reduction. These samples were then ground into spheres and polished with successively finer grit abrasives. An exponential decrease in the linewidth was observed as a function of grit size. Linewidth measurements were made using the standard cavity perturbation technique. The diameters of the samples ranged from 0.018 to 0.030 in. (450 to 750 μ). The orientation of spheres in the cavity was such that the microwave magnetic field and the applied field were perpendicular to each other and in the plane of easy magnetization of the material.