M. A. Popov

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.

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).

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.

Magnetostatic oscillations in transversely biased long ferromagnetic cylinder of elliptical cross-section

The analytical theory describing magnetostatic oscillations in a transversely magnetized infinitely long ferromagnetic cylinder of elliptic cross-section has been developed. The implicit equation for the eigenfrequencies of modes has been derived and analyzed. An example of frequency spectrum of an elliptic cylinder with a/b=2 was presented. Magnetostatic potential of the eigenmodes in form of elementary functions has been found, that will allow obtaining simple analytical expressions for spatial distribution of the high-frequency magnetization.

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.

Non-destructive technique for magnetic material parameter measurements

A non-destructive local technique for magnetic material parameter measurements was developed and used for relaxation properties of barium hexaferrite investigation. The obtained value of relaxation frequency is in reasonable agreement with previously reported values.

Coupled Electromagnetic and Magnetostatic Oscillations in Hexaferrite-Dielectric Structures

Coupled electromagnetic-magnetostatic oscillations over 60-75 GHz in strontium hexaferrite-quartz structures have been investigated. Data regarding the frequencies and Q-factor of the modes have been obtained as a function of the bias magnetic field and quantitatively analyzed using Aulds approach.