I. V. Zavislyak

Splitting axially heterogeneous modes in microwave gyromagnetic and gyroelectric resonators

Theory of calculating eigenmodes spectrum for gyrotropic resonators when using scalar potentials formalism is developed. Equations for calculating splitting of resonant frequencies of gyromagnetic and gyroelectric cylinder resonators in magnetic field are derived. Theoretical results are compared to the experimentally obtained figures for microwave gyromagnetic resonators made of barium hexaferrite. Example of a resonator made of indium antimonide demonstrates the possibility of using magnetized semiconductor resonators cooled to liquid nitrogen temperature to achieve the same characteristics offered by resonators made of magnetically firm hexaferrites when designing unidirectional microwave devices.

Mode Splitting in 37–42 GHz Barium Hexaferrite Resonator: Theory and Device Applications

Dielectric resonances in the 37-42 GHz frequency band in the single crystal barium hexaferrite that occur well below the ferromagnetic resonance (FMR) have been investigated. Sample dimensions have been chosen so that the mode frequency is lower than the spin-wave excitation (in this case, the natural domain resonance) frequency. Such dielectric mode frequencies, being a function of both permittivity and permeability, are magnetic field H tunable. Here, we report on below-FMR magnetodielectric resonance (MDR) axially magnetized barium hexaferrites and their H-tuning characteristics. Our studies reveal H-tuning by up to 2.5 GHz and the tuning is the largest when the ferrite is in a magnetically unsaturated state. A theory for the MDR is presented and a fairly good agreement between experimental data and theory has been obtained. Tunable millimeter wave phase shifters and isolators utilizing the below-FMR dielectric resonances have been demonstrated.

Ferromagnetic resonance in a single crystal of iron borate and magnetic field tuning of hybrid oscillations in a composite structure with a dielectric: Experiment and theory

The high-frequency properties of a composite resonator comprised single crystal iron borate (FeBO3), a canted antiferromagnet with a weak ferromagnetic moment, and a polycrystalline dielectric were investigated at 9–10 GHz. Ferromagnetic resonance in this frequency range was observed in FeBO3 for bias magnetic fields of ∼250 Oe. In the composite resonator, the magnetic mode in iron borate and dielectric mode are found to hybridize strongly. It is shown that the hybrid mode can be tuned with a static magnetic field. Our studies indicate that coupling between the magnetic mode and the dielectric resonance can be altered from maximum hybridization to a minimum by adjusting the position of resonator inside the waveguide. Magnetic field tuning of the resonance frequency by a maximum of 145 MHz and a change in the transmitted microwave power by as much as 16 dB have been observed for a bias field of 250 Oe. A model is discussed for the magnetic field tuning of the composite resonator and theoretical estimates a...

Dual electric and magnetic frequency tuning of coupled oscillations in a composite magnetodielectric resonator

The possibility of dual magnetic and electric tuning of resonance frequencies of the electrodynamic structure consisting of dielectric resonator and the epitaxial film of Yittrium-Iron Garnet (YIG)- lead zirconate titanate (LZT) heterostructure has been shown. The coupled electromagnetic-andspin oscillations of dielectric resonator and epitaxial YIG film were theoretically and experimentally investigated. The experiments revealed the possibility of implementing the electric frequency tuning of coupled oscillations of a composite magnetodielectric resonator. This possibility is determined by induced elastic stresses in the epitaxial YIG film. A theoretical model is proposed for calculating the frequency shift of coupled oscillations caused by the electric field applied to the piezodielectric layer. It is shown that the basic Q-factor of composite resonator and the range of electric frequency tuning of hybrid oscillations increase with the reduction of the magnetic bias field.

Simultaneous observation of magnetostatic backward volume waves and surface waves in single crystal barium ferrite platelets with in-plane easy axis

Resonances corresponding to backward volume magnetostatic waves as well as magnetostatic surface waves have been observed in single crystal barium hexaferrite rectangular platelets with in-plane easy axis. Samples placed directly on waveguide wall or on a quartz substrate show a surface mode. A series of backward volume wave modes in the U-band are observed, with the sample placed on quartz showing a relatively few modes. Data on H-dependence of the mode frequency have been obtained for both kinds of magnetostatic waves and theoretical estimates of the mode frequencies are in reasonable agreement with the data. Quality-factor for the modes is in the range 400-750. The results are of interest for non-reciprocal ferrite devices in the U-band.

Electric field induced non-linear magnetoelectric effects in M-type single crystal strontium hexaferrite

This report is on the first observation of non-linear magnetoelectric (ME) effects in single crystal platelet of M-type strontium hexaferrite, SrFe<inf>12</inf>O<inf>19</inf> (SrM).

Frequency splitting effect of degenerate modes in ferrite resonators

The splitting of magneto-dielectric modes frequency in disk ferrite resonators in a magnetic field is considered.Asimplified formula is obtained for estimation of the splitting magnitude. Theoretical and experimental results of the frequency splitting effect in magneto-dielectric modes in the millimeter wave range are compared. The use of the splitting of the magneto-dielectric modes frequencies as an alternative to ferromagnetic resonance in devices with magnetic frequency tuning is suggested, with values of the magnetization fields being an order of magnitude lower than for ferromagnetic resonance. The features of the splitting modes effect in different ferrite classes are investigated and it is shown that it occurs in both microwave and optical ranges. The estimated magnitude of the mode frequency splitting in the iron-yttrium garnet (YIG) transparency window can reach 9 GHz, which is comparable to the 5 GHz splitting in the millimeter range. The frequency ranges where frequency splitting effect is of practical interest are discussed. In particular, the effect in barium hexaferrite can be used both in post-resonance and pre-resonance regions, which is almost impossible for ferrogarnates and ferrospinels.

Passive ferrite resonator-based millimeter wave band components

The review of magnetodynamic resonances in ferrite resonators and their mm-wave band applications was given. Ferrite resonator eigenexcitations classification has been presented. The analytical theory for modes resonant frequencies calculations is stated and a number of prototype electronically tunable mm-wave devices, utilizing the “above” and “below FMR” magnetodynamic resonances, including isolator, phase shifter, band-pass and band-stop filters have been demonstrated.

Ferrite-dielectric resonators made of uniaxial ferrites in before-the-resonance region

Theeffect of splitting resonant frequencies of azimuthally heterogeneousHE±11δ oscillations of a disc ferrite-dielectric resonator made of barium hexaferrite is studied in external magnetic field on frequencies below 47 GHz. Applicability of the developed earlier analytical theory of electromagnetic oscillations in magneto-gyrotropic resonators to mode identification and calculation of field dependencies of magnetic oscillations’ resonant frequencies in the before-the-resonance region is demonstrated. Hysteresis effect is discovered in the field dependencies of magneto-dynamic oscillations’ eigenfrequencies in resonators made of uniaxial ferrite. The influence of dielectric layer between the resonator and the metal screen on frequency splitting of HE±11δ oscillations is studied. The possibility of using ferrite-dielectric resonators in the self-magnetization mode is discussed.

A tunable hexaferrite dielectric resonator for W-band devices

Magnetic field tuning characteristics of a single-crystal barium hexaferrite dielectric resonator in the frequency range 75-110 GHz are reported. The dielectric resonances occur at a much higher frequency than the ferromagnetic resonance. It is shown that the degeneracy in the dielectric mode is lifted with an applied magnetic field H and that the modes can be tuned by 10 GHz or more with H. The dielectric modes are of importance for the realization of low-loss devices, including resonators, isolators and phase shifters.