S. I. Khartsev

Epitaxial ferroelectric/giant magnetoresistive heterostructures for magnetosensitive memory cell

Epitaxial ferroelectric/giant magnetoresistive Pb(Zr0.52Ti0.48)O3/La0.67Ca0.33MnO3 (PZT/LCMO) heterostructures have been grown onto LaAlO3 (001) single crystal by KrF pulsed laser deposition. Main processing parameters have been optimized to preserve giant magnetoresitivity in the LCMO film after deposition of the top ferroelectric layer. High degree of c-axis orientation and strong in-plane texture, coherent with the substrate, both in template LCMO and PZT layers, high dielectric permittivity of 720, remnant polarization of 17 μC/cm2 of PZT, and magnetoresistivity in LCMO of 28% at H=0.5 T indicate excellent characteristics of coexisting magnetoresistive and ferroelectric properties. We compare the performance of magnetosensitive memory cells with La0.67Ca0.33MnO3 and La0.75Sr0.25MnO3 giant magnetoresistive electrodes.

Microwave and magneto-optic properties of pulsed laser deposited bismuth iron garnet films

We report on processing and comparative characterization of epitaxial Bi/sub 3/Fe/sub 5/O/sub 12/ (BIG) films grown by pulsed laser ablation of a precursor oxide target onto (NdGd)/sub 3/(ScGa)/sub 5/O/sub 12/ [NGSGG[111]] and Gd/sub 3/(ScGa)/sub 5/O/sub 12/ [GSGG[001]] single crystals. Comprehensive X-ray diffraction analyses reveal the epitaxial quality of the BIG films: they are single phase, exclusively [111] and [001] oriented with less than 0.4/spl deg/ and 0.06/spl deg/ of the full width at half maximum of the rocking curve of main texture Bragg reflection [[111] for NGSGG and [001] for GSGC substrate, respectively]. The films are strongly in-plane textured with cube-on-cube film-to-substrate epitaxial relationship. VSM and ferromagnetic resonance measurements revealed in-plane magnetization in BIG/GSCG[001] film, while the BIG/NGSGG[111] film was found to have perpendicular magnetization. For BIG[001] and [111] films the saturation magnetization 4/spl pi/M/sub s/ was found to be 1400 and 1200 Gs; the Faraday rotation at 635 nm was -7.8 and -6.7 deg//spl mu/m; the constant of uniaxial magnetic anisotropy was K/sub u/*=-8.70/spl times/10/sup 4/ and +1.16/spl times/10/sup 4/ erg/cm/sup 3/; the constant of cubic magnetic anisotropy K/sub 1/=-3.6/spl times/10/sup 3/ and -7.14/spl times/10/sup 3/ erg/cm/sup 3/. High Faraday rotation and low coercive field (/spl les/40 Oe) of BIG/GSGG[001] films show promise for their use in integrated magneto-optic applications.

High performance latching-type luminescent magneto-optical photonic crystals

We report the properties of one-dimensional heteroepitaxial all-garnet magneto-optical photonic crystals (MOPCs) composed of alternating quarter-wavelength layers of diamagnetic Sm(3)Ga(5)O(12) and MO-active Bi(2.97)Er(0.03)Al(0.5)Ga(0.5)O(12) garnets rf-magnetron sputtered on Gd(3)Ga(5)O(12) (111) substrate. Substitution of ferric ions by aluminum and gallium improved transparency and induced perpendicular anisotropy in pure bismuth iron garnet. As a result, photonic crystals owned a record high magneto-optical quality and a latching-type (magnetic remnant) Faraday rotation (FR). At the resonance wavelengths 775(640) nm, a specific FR(θ)(F)=-14.1(14.8) deg/μm and MO-quality factor Q=99.3(46.2) deg represent the highest MOPC performance achieved so far.

Comparative Characteristics of Na0.5K0.5NbO3 Films on Pt by Pulsed Laser Deposition and Magnetron Sputtering

Ferroelectric Na0.5K0.5NbO3 (NKN) thin films were grown on the Pt80Ir20 polycrystalline substrates by pulsed laser deposition (PLD) and radio frequency-magnetron sputtering (RF) technique using the same stoichiometric Na0.5K0.5NbO3 ceramic target. X-ray diffraction proved both PLD- and RF-made Na0.5K0.5NbO3/Pt80Ir20 films are single phase and have preferential c-axis orientation. Temperature dependence of dielectric permittivity reveals the presence of two phase transitions around 210 and 410°C. Capacitance vs. applied voltage C-V @ 100 kHz, I-V, and P-E hysteresis characteristics recorded for the vertical capacitive structures yielded loss tanδ = 0.026 and 0.016, tunability about 44.5 and 30% @ 100 kV/cm, Ohmic resistivity 6.7 × 1012 Ω·cm and 0.2 × 1012 Ω·cm, remnant polarization 11.7 and 9.7 μC/cm2, coercive field 28.0 and 94.6 kV/cm for PLD- and RF-films, respectively. Piezoelectric test carried out in hydrostatic conditions showed piezoelectric coefficient d H = 21 for PLD-NKN and 15 pC/N for RF-NKN film.

Ferroelectric Bi4Ti3O12 thin films on Pt-coated silicon by halide chemical vapor deposition

A halide chemical vapor deposition technique has been developed to grow highly c-axis oriented submicron Bi4Ti3O12 films onto Pt(200 nm)/Ti(20 nm)/SiO2(1200 nm)/Si(100) substrates. BiI3, TiI4, and ...

Preparation of Na 0.5 K 0.5 NbO 3 /La 0.6 Sr 0.2 Mn 1.2 O 3 /LaAlO 3 Thin Film Structures by Pulsed Laser Deposition

We report on ferroelectric/giant magnetoresistive Na 0.5 K 0.5 NbO 3 /La 0.6 Sr 0.2 Mn 1.2 O 3 (NKN/LSMO) heterostructures grown onto LaAlO 3 (001) single crystal using KrF pulsed laser ablation of stoichiometric ceramic target. Main processing parameters have been optimized to obtain smooth LSMO template layer, avoid NKN-LSMO interdiffusion, preserve NKN stoichiometry against the lost of volatile potassium and sodium and achieve reasonable reliability of NKN film performance. X-ray diffraction θ- 2θ scans and rocking curves evidence for single-phase content and high c-axis orientation both in template LSMO and top NKN layers. Ferroelectric measurements yield remnant polarization P r of 1.5 [C/cm 2 and spontaneous polarization P s of 7 μC/cm 2 at electric field strength of 130 kV/cm. At room temperature, dielectric permittivity e′ and dissipation factor tan δ have been found to vary from 595 to 555 and 0.046 to 0.029 respectively in the frequency range of 0.4 to 20 kHz. At 10 kHz dielectric permittivity linearly increases from 410 to 650 in the temperature range 77 K to 415 K while the dissipation factor below 320 K does not exceed 3%.

Ferromagnetic Resonance in Single Crystal Bismuth Iron Garnet Films

Among other magneto-optic materials bismuth substituted yttrium iron garnet (Bi x Y 1−x ) 3 Fe 5 O 12 has the highest Faraday rotation effect in visible region. Completely substituted bismuth iron garnet Bi 3 Fe 5 O 12 (BIG) films have been grown by pulsed laser deposition technique onto (111) (NdGd) 3 (ScGa) 5 O 12 single crystal with lattice constant of 12.623 A. X-ray diffraction proves epitaxial film quality. VSM measurements yield the saturation magnetization 4π M s , = 1100 G and coercive field is about 50 Oe. Ferromagnetic resonance (FMR) method reveals perpendicular magnetic anisotropy in fabricated films. Angular measurements of FMR give the constants of uniaxial and cubic anisotropy in BIG film: K u = 5.9×10 4 erg/cm 3 and K 1 = - 6.95×10 3 erg/cm 3 . The Faraday rotation has been found to reach - 7.8 deg/µm at 630 nm.

Colossal magnetoresistive thin films for uncooled bolometer

Pulsed laser deposition technique has been employed to fabricate a continuous series of solid solutions with basic composition of La0.7(Pb1- xSrx)0.3MnO3, which undergo metal-to-insulator transition near the room temperature. These films exhibit colossal magnetoresistivity (CMR) and strong temperature dependence of resistivity in the vicinity of phase transition. Temperature coefficient of resistivity (TCR) has been tailored by precise compositional control tog et maximum value close to room temperature. Film with TCR as high as 7.4%K1 at 295 K and magnetoresistance of 30% at 7kOe has been used to make uncooled bolometer demonstrator. The responsivity as high as 0.6 V/W, noise equivalent power of 3x10-8W/(root)Hz, detectivity of 9x106 cm(root)Hz/W, and noise equivalent temperature difference as low as 120 nK/(root)Hz at 30 Hz frame frequency have been achieved for non-optimized bolometer based on 4.5-micrometers - thick film grown on 2.5x2.5x0.5 mm3 LaAlO3(001) substrate. Measurements of optical responsivity in frequency and time domains yield substrate-to-thermostat thermal conductance G = 3x10-3 W/K and three relaxation times responsible for heat transfer from film thermistor to substrate, from substrate to thermostat, and heat exchange via leads to be 0.5 s, 1.9 ms and 90 microsecond(s) correspondingly. Improving bolometer design by micromachining technique, one can expect that reducing of thermal conductance G down to 10-6 W/K for bolometer with resistance of 500 (Omega) , should result in the increasing of responsivities to 3.9 A/W and 2.8x103 V/W and detectivities to 2.5x108 cm(root)Hz/W and 9.3x108 cm(root)Hz/W at 30Hz in voltage and current biasing regime correspondingly.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Luminescence in epitaxial Er-doped LiNbO 3 films

Epitaxial Er-doped LiNbO3 films were pulsed-laser-deposited onto c-cut sapphire. Wavelength dispersion of the refractive index and the extinction coefficient was obtained by fitting the experimental transmittance spectrum to the Swanepoel formula and microscopic theory, which accounts for two resonance transitions in the electric dipole approximation. Strong room temperature luminescence was observed under 514.5 nm Ar-laser pumping. Two-lifetime (3.0 and 6.0 ms) luminescent decay is characteristic for the lasing 4I13/2→4I15/2 transition in Er:LiNbO3 films.

Enhanced photoluminescence in [Er2O3/TiO2]m photonic crystals

We survey optical properties of [Er2O3/TiO 2]6/Er2O32/[TiO 2/Er2O3]6 photonic crystals (PCs) pulsed laser deposited on to the glass substrates. The dispersion relations of refractive indexes and ex ...