Microwave Relaxation and Microstructure in Polycrystalline Ferrites.
Final rept. 1 Sep 74-30 Sep 77,
COLORADO STATE UNIV FORT COLLINS DEPT OF PHYSICS
Pagination or Media Count:
The relationship between microstructure and microwave loss in polycrystalline ferrites has been investigated. Two classes of materials were used, polycrystalline yttrium iron garnet YIG with a systematic variation in porosity and grain size and arc-plasma-sprayed Li-Ti ferrite. Data include magnetization versus field at room temperature, near-resonance and off-resonance effective linewidth as functions of temperature from 100 K to 300 K at 10 GHz, and parallel pump spin-wave linewidth as a function of wave-number at 9 GHz, for temperatures from 90 K to 370 K. The data indicate that neither the transit-time nor the magnetostriction mechanism are reasonable sources of the intrinsic microwave losses in polycrystals. The YIG effective linewidth data suggest the importance of small second phase content, possibly in the grain boundaries, with a Curie temperature on the order of 300 K. The YIG high power data indicate that the mechanisms controlling the spin-wave linewidth are quite different from those limiting the effective linewidth. Significant increases in spin-wave linewidth occur at low temperature, while the effective linewidth is relatively constant at low temperature. The data on the Li-ferrite materials prepared by the arc-plasma-spraying process indicate that this novel process is potentially of great value in the production of practical materials for radar applications.
- Electrical and Electronic Equipment