Performance and Ferrimagnetic Material Considerations in Cryogenic Microwave Devices

Abstract

Circulators which can be operated at cryogenic temperatures are discussed. Both symmetrical Y-junction circulators using polycrystalline ferrimagnetic garnets and hybrid-gyrator circulators using single crystals are evaluated. The temperature dependence of the ferromagnetic resonance losses of polycrystalline aluminum-doped and undoped yttrium iron garnet is reported. Device performance is evaluated in terms of the measured material properties.

Microstrip superconducting resonators loaded with yttrium iron garnet single crystals

“…7 and 8. However, in the YIG single crystal, we can assume limited low temperature dependence of DH, based on the reference to the characteristics of a YBCO circulator [12]. On the other hand, when we performed similar experiments with polycrystalline YIG instead of a single crystal, a low Q L of 50 and a narrow tunability of 110 MHz were observed at 77 K.…”

Microstrip superconducting resonators loaded with yttrium iron garnet single crystals

“…5 and 7, we can see ripples around 5.2 GHz from the resonance characteristics. However, in the YIG single crystal, we can assume limited low temperature dependence of DH, based on the reference to the characteristics of a YBCO circulator [12]. The resonant frequency of f 0 is varied by changing the applied magnetic field at the rate of 0.3 MHz/Oe.…”

Temperature Effects on the Performance Characteristics of an Above-Resonance Junction Circulator

“…The distinct increase in insertion loss in the device with Dy and Al-Gd YIG and also the tendency of loss increase at lower temperatures may be related to the variation in effective Iinewidth of the material over the operating conditions. The probable explanation for such loss increases at lower temperatures is that, linewidth of such materials broadens at lower temperatures (Comstock et al 1965). Also the increase in losses with doping is due to the fact that the resonance line-widths vary from 45 Oe to 95 Oe with different doping (Vrehen 1969).…”