ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Large magnetocrystalline anisotropy makes hexagonal ferrites attractive for microwave and millimeter wave applications. Critical to such applications is the response at high power levels. Relatively little work has been reported in this area. In order to characterize this response, the minimum microwave field amplitude required to excite spin–wave instability, hcrit, is measured for various field–sample configurations. Plots of hcrit versus static field H, termed "butterfly" curves, are then used to obtain spin wave linewidths and define operational power limits for device applications. Two regimes were studied in this work: (1) saturation of the ferromagnetic resonance (FMR) absorption; and (2) parallel pumping instability for fields well below FMR. The objective was to measure butterfly curves and use the results to determine values of the spin–wave linewidth ΔHk. The measurements were made on a 1.2 mm diam 0.15 mm thick single-crystal Mn substituted Zn2Y (Y-type) hexagonal ferrite c-plane (001) disk with easy plane anisotropy. The static field and the 4 μs wide, 30 Hz pulsed microwave field at 8.9 GHz were applied in the plane of the disk. Standard cavity techniques were used. The low power ferromagnetic resonance (FMR) linewidth was 15 Oe. For resonance saturation, the measured hcrit was 0.29 Oe at the FMR field of 775 Oe. The resonance saturation butterfly curve was asymmetric about its minimum value at FMR. The hcrit for parallel pumping was approximately 5 Oe and independent of H over the range of 150–350 Oe. These data and spin–wave instability theory were used to estimate ΔHk values. For parallel pumping, ΔHk was determined to be 17 Oe for the critical modes at one half the 8.9 GHz pump frequency. For resonant saturation, ΔHk was determined to be 12 Oe for the critical modes at the pump frequency. © 1997 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.364890
Permalink
