A. S. Tatarenko

Millimeter-wave magnetoelectric effects in bilayers of barium hexaferrite and lead zirconate titanate

Millimeter-wave magnetoelectric interactions have been studied through electric field effects on magnetic excitations in bilayers of single crystal barium ferrite and lead zirconate titanate (PZT). An electric field E produces a mechanical deformation in PZT, resulting in a shift δf in the frequency for electromagnetic modes in the ferrite. Reflected power versus frequency profiles at 40–55GHz for a series of bias magnetic field and E=0–10kV∕cm along the c axis of the ferrite showed an increase in δf to a maximum of 8MHz. Theoretical estimates of δf are in agreement with the data.

Al substituted Ba-hexaferrite single-crystal films for millimeter-wave devices

Microwave and magnetic properties of single-crystal aluminum substituted barium hexaferrites BaAlxFe12−xO19 with Al substitution level x from 0 to 2 are reported. The single crystals were grown by the floating zone melting method. Films in the form of 100 μm thick, 1 mm wide, and 2 mm long resonators were used for ferromagnetic resonance (FMR) measurements in the frequency domain over 40–110 GHz for applied magnetic fields of 0–10 kOe. Based on these measurements, the hexaferrite parameters are determined. With increasing x from 0 to 2, the uniaxial magnetocrystalline anisotropy field increases from 17.88 to 33.68 kOe, while reasonable values of full FMR linewidth (35 Oe at 47 GHz and 140 Oe at 108 GHz) are maintained. These parameters ensure the potential for use of the ferrites in millimeter-wave devices.

Size-controlled one-dimensional monocrystalline BaTiO3 nanostructures

One-dimensional BaTiO3 nanostructures have been synthesized by a simple hydrothermal ion-exchange reaction using alkali-metal titanates as synthetic precursors. The BaTiO3 nanowires obtained from Na2Ti3O7 nanowires have diameters of 50–80 nm and lengths of up to 10 μm. In contrast, BaTiO3 nanowires obtained from K2Ti4O9 nanowhiskers have relatively large sizes of 300–500 nm in diameter and several tens of microns in length. Both types of nanostructures are single-crystalline without any impurity phases. The local electric polarization of individual ferroelectric nanowires has been studied using vertical mode piezoresponse force microscopy.

Microwave magnetoelectric effects in bilayers of piezoelectrics and ferrites with cubic magnetocrystalline anisotropy

The strain mediated microwave magnetoelectric coupling is studied in bilayers of ferrites with cubic anisotropy and piezoelectrics. The strength of magnetoelectric coupling is determined from data on ferromagnetic resonance frequency shift Δf versus applied electric field E. Studies at 6–10 GHz on samples of nickel zinc ferrite and polycrystalline lead zirconium titanate, lead magnesium niobate–lead titanate or lead zinc niobate-lead titanate (PZN–PT) show shifts Δf on the order of 30–150 MHz for E=10 kV/cm. Bilayers of nickel zinc ferrite and PZN-PT demonstrated the highest magnetoelectric coefficient of 5.3 Oe cm/kV. Theoretical estimates of the frequency shifts are in very good agreement with the data.

Magnetic and Dielectric Excitations in the W-Band in Aluminum Substituted Barium and Strontium Hexaferrites

Single crystal strontium and barium hexaferrites in which Al is substituted for Fe have uniaxial anisotropy fields on the order of 20-30 kOe and have magnetic excitations at 75-110 GHz. Here, we discuss results of investigations on magnetostatic forward volume waves and dielectric resonances in such ferrites. Data on the mode frequencies were utilized to characterize the ferrites in terms of saturation magnetization, anisotropy field, gyromagnetic ratio, dielectric permittivity, and dielectric and magnetic losses. A refined theory of magnetostatic forward volume waves with explicit characteristic equation for the dominant mode is presented. The estimates on the mode characteristics are in very good agreement with the data.

Electrically-tunable microwave phase shifter based on ferrite-piezoelectric layered structure

A new class of electrically tunable microwave signal processing devices based on layered ferrite-piezoelectric structure is proposed. A trilayer magnetoelectric structure consisting of a lead magnesium niobate-lead titanate (PMN-PT) and yttrium iron garnet (YIG) film on gadolinium gallium garnet (GGG) substrate is considered. Design and experimental data of microstrip phase shifter are presented.

Electric field induced broadening of magnetic resonance line in ferrite/piezoelectric bilayer

The present investigation focuses on magnetoelectric interactions in ferrite-piezoelectric bilayers in the ferromagnetic resonance (FMR) region. A dc electric field applied perpendicular to the sample plane gives rise to an in-plane strain that is transferred to the ferrite and produces a uniaxial thickness-dependent magnetic anisotropy. Expressions for microwave magnetic susceptibility are obtained taking into account the effects of flexural deformations. The results are applied to the specific case of yttrium iron garnet (YIG)/lead zirconate titanate (PZT). The study predicts the unique electric field dependence of FMR line broadening. For the specific YIG to PZT thickness ratio, magnetoelectric coupling results in a weak FMR line shift and considerable line broadening. The results are of interest for novel ferrite-piezoelectric microwave devices.

Magnetoelectric Tunable Microwave Band-Pass Filter

-Magnetoelectric band-pass filters based on ferrite-piezoelectric structure covering the frequency bands 5 to 10 GHz have been designed and characterized. Descriptions of devices which can be tuned by both electric and magnetic fields at microwave frequencies are given and experimental data are presented showing their tuning range, insertion loss, and other characteristics.

Microwave magnetoelectric devices

One of prospective directions of solid-state electronic engineering is to produce new devices on the basis of magnetoelectric materials. The design and application of a new microstrip microwave filter and attenuator based on composite ferrite-piezoelectric resonators are considered.