Jaydip Das

In-plane c-axis oriented barium ferrite films with self-bias and low microwave loss

Hybrid pulse laser deposition and liquid phase epitaxy methods have been used to produce in-plane c-axis (IPCA) oriented barium ferrite (BaM) films on a-plane (112¯0) sapphire substrates with low microwave loss and a high remanence. Total thicknesses were from 5to20μm. A reasonable compromise for low loss and high remanence was reached at a thickness of 7μm, with a remanence ratio of 0.84 and a 59GHz peak-to-peak derivative linewidth of 250Oe. The 20μm thick film had a linewidth of 110Oe, one of the smallest values ever obtained for IPCA BaM films.

Electric field tunable 60 GHz ferromagnetic resonance response in barium ferrite-barium strontium titanate multiferroic heterostructures

A magnetic-ferroelectric film heterostructure with a large electric field tuning of the ferromagnetic resonance (FMR) mode was fabricated. Pulse laser deposited 30 nm thick Pt electrodes and 3 μm thick barium strontium titanate films on Nb-doped strontium titanate substrates were capped with an unbonded 200 μm thick single crystal in-plane c-axis barium hexaferrite slab. The structure gives a 60 GHz FMR frequency shift of 16 MHz at a bias of 29 V, for an average response of 0.55 MHz/V. The maximum incremental tuning response at 29 V was 1.3 MHz/V. This is a hundredfold improvement over previous results.

Multifunctional dual-tunable low loss ferrite-ferroelctric heterostructures for microwave devices

Oriented barium ferrite (BaM) and polycrystalline ferroelectric barium strontium titanate (BSTO) layered structures have been fabricated by pulsed laser deposition. The 0.5μm thick BaM layer has a saturation induction of 4kG, a uniaxial effective anisotropy field of 16kOe, and a relatively low ferromagnetic resonance linewidth of about 25Oe, values that are indicative of a high quality film. The dielectric constant of the 0.9μm thick BSTO layer drops by a factor of 2 for an applied voltage of 3V.

Static and high frequency magnetic and dielectric properties of ferrite-ferroelectric composite materials

A series of sintered composite materials was fabricated from Parascan™ barium strontium titanate (BSTO) and Trans-Tech nickel zinc ferrite powders. The ferrite loading was varied from zero (BSTO only) to 100wt% (ferrite only). X-ray diffraction data show the presence of a third, nonmagnetic phase that sets the ferrite loading at values somewhat lower than the as prepared wt % amounts. The average magnetization is found to scale linearly with the loading. The initial susceptibility, saturation field, and coercive force as obtained from hysteresis loop data show trends consistent with these data. Ferromagnetic resonance linewidth and effective linewidth measurements at 10GHz show reasonable values for the 100wt% samples, but any amount of BSTO causes a severe degradation in both loss parameters. Similarly, it is found that any amount of ferrite causes a rapid drop in the relative dielectric constant that is consistent with standard mixing models. Loss tangent measurements gave modest values in the 0.001–0.0...

Large dielectric tuning and microwave phase shift at low electric field in epitaxial Ba0.5Sr0.5TiO3 on SrTiO3

Dielectric properties of annealed and as-grown ferroelectric Ba0.5Sr0.5TiO3 (BST) grown by pulsed laser deposition on sputtered BST seed layers on strontium titanate (STO) substrates were investigated at microwave frequencies in the realm of tunability of its dielectric constant as well as phase shifters based on this material. The as-grown layers were nearly fully relaxed with measured lattice parameters nearly identical to those of bulk BST. The tuning of the relative dielectric constant (∼1750 at zero bias at 10 GHz) of the annealed BST was found to be as high as 59% and 56% at 10 and 19 GHz, respectively. The analysis of the loss in the BST results in a measured tan δ of 0.02 for the annealed as well as the unannealed films at a frequency of 18 GHz. Phase shifters also exhibited high tuning with differential phase shift figures of merit of 35 and 55°/dB at a field of 60 kV/cm at 10 and 19 GHz, respectively. Serendipitously, most of the tuning occurs at low fields, and thus we propose a new figure of m...

Magnetic properties and structural implications for nanocrystalline Fe-Ti-N thin films

The magnetization and ferromagnetic resonance (FMR) profiles have been measured for a series of soft-magnetic nanocrystalline

Electric-field control of ferromagnetic resonance in monolithic BaFe12O19–Ba0.5Sr0.5TiO3 heterostructures

\mathrm{Fe}\text{\ensuremath{-}}\mathrm{Ti}\text{\ensuremath{-}}\mathrm{N}

Electric Tuning of Ferromagnetic Resonances in Hexagonal-Barium-Ferrite/Barium-Strontium-Titanate Heterostructures

films. Magnetization

Intergranular Interactions and Thermal Stability in Fe–Ti–N Thin Films

(M)

Intergranular Interactions in Fe-Ti-N Thin Films

measurements were made as a function of temperature