Low-Temperature Nonlinear Effects in High-Saturation Magnetization Ferrites

Abstract

Single-crystal nickel zinc (Ni0.5Zn0.5Fe2O4) and lithium zinc (Li0.35Fe2.35Zn0.5O4) ferrite were used in an experimental investigation of ferromagnetic nonlinear effects with incident power at both room temperature and 77°K. All data were taken at a constant frequency of 9.0 GHz. The lowest measured linewidths (ΔH) were 10 and 15 Oe at room temperature on nickel zinc and lithium zinc, respectively. These linewidths are reduced approximately 50% at 77°K. The saturation magnetization of the samples was in the order of 5000 ±150G at room temperature. This magnetization is increased approximately 20% above the room temperature value at 77°K. Variation of the incident power in oersteds over the range 1×10−6 to 10 Oe yielded the following general results: A substantial reduction in threshold field for nonlinear effects was measured on both lithium and nickel zinc ferrite at 77°K. Spin-wave linewidths (ΔHk) calculated at 77°K also yielded large reductions from those observed at room temperature. These enhanced values of saturation magnetization, along with the low threshold fields observed in nickel zinc ferrite, have important applications in the design of microwave-power limiters operating in the coincidence mode.