Resonance Experiments with Single Crystal Yttrium Iron Garnets in Pulsed Magnetic Fields

Abstract

A crystal sphere of YIG was placed in either a doubly resonant transmission type coaxial cavity or into a nonresonant transmission line device and biased with a dc magnetic field. A low power microwave signal in the S band frequency range (cw or pulsed) was used to excite resonance. Current pulses of approximately 1 μsec duration and low duty cycle were sent through a low impedance coil that was wound around the cavity or transmission line respectively. These pulses induced pulsed magnetic fields of the order of 1000 gauss, which (vectorially) added to the existing dc field. A microwave receiver, attached to the cavity output, detected weak oscillations at higher or lower frequencies. Shifts of 280 Mc have been obtained with the cavity, and shifts of 1280 Mc above and 530 Mc below the driving frequency have been obtained with the transmission type device. The detected signal is associated with either the rise of the current pulse, or the decay, or two signals may appear simultaneously corresponding respectively to the rise and decay. This depends upon the angular relation of the dc field with respect to the cavity or transmission line.