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22 Jan 2007

Volume 90, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 90, 043507 (2007); http://dx.doi.org/10.1063/1.2435508 (3 pages)

D. Y. Kim and A. J. Steckl
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Silicon oil: A cheap liquid additive for enhancing in-field critical current density in MgB2

X. L. Wang, Z. X. Cheng, and S. X. Dou

Appl. Phys. Lett. 90, 042501 (2007); http://dx.doi.org/10.1063/1.2435321 (3 pages) | Cited 24 times

Online Publication Date: 23 January 2007

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In this work, the authors report on significant flux pinning enhancement in MgB2 that has been easily obtained using a liquid additive, silicon oil. MgB2 bulk samples with 0 up to 30 wt % silicon oil added were prepared by an in situ reaction. Results showed that the Si and C released from the decomposition of the silicon oil formed Mg2Si and substituted into B sites, respectively. Increasing the amount of the Si oil up to 15 wt % has resulted in the reduction of the lattice parameters, as well as Tc and R(300 K)/R(Tc) values, accompanied by a significant enhancement of Jc(H), Hirr, and Hc2.
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74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
61.66.Fn Inorganic compounds
61.72.up Other materials

Structure and magnetic transport properties of Ge doped La(Co,Si)13 intermetallics

Yongquan Guo and Wei Li

Appl. Phys. Lett. 90, 042502 (2007); http://dx.doi.org/10.1063/1.2435331 (3 pages)

Online Publication Date: 23 January 2007

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The crystal structure and the magnetic and electronic transport properties of Ge doped LaCo10.5Si2.5−xGex (x = 0–0.3) intermetallics have been investigated using powder x-ray diffraction and magnetic and electrical measurements. According to the x-ray diffraction pattern analysis, Ge as a dopant decreases the stability of the cubic LaCo 1:13 phase and stabilizes the Si based La(Co,Si) 1:13 tetragonal phase. From the authors’ structural refinement, the authors found that Ge prefers to occupy the 16l(2) position in the tetragonal phase. LaCo10.5Si2.2Ge0.3 shows ferromagnetic order with a metamagnetic state around 350 K. An anomaly in resistivity is observed at around 367 K, which is associated with the metamagnetic transition. The resistivity follows ρ(T) = ρo+aTn rule in the temperature range of 4–400 K with n = 1.17(3) for the half metallic state and n = 2 for the normal metallic state, respectively. This type of discontinuity can be interpreted as a crossover from a low temperature metamagnetic half metallic state to the normal ferromagnetic-metallic state.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Cc Other ferromagnetic metals and alloys
61.66.Dk Alloys
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys

Optimizing levitation force and stability in superconducting levitation with translational symmetry

Nuria Del Valle, Alvaro Sanchez, Enric Pardo, Du-Xing Chen, and Carles Navau

Appl. Phys. Lett. 90, 042503 (2007); http://dx.doi.org/10.1063/1.2435940 (3 pages) | Cited 22 times

Online Publication Date: 23 January 2007

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From a theoretical analysis based on an energy minimization procedure and the critical-state model, the authors analyze the levitation of an infinitely long superconductor above infinitely long permanent magnets with different arrangements. A discussion on optimum geometries showing large levitation force and good stability is presented from the model results.
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74.25.Ha Magnetic properties including vortex structures and related phenomena

Ultrafast magnetization dynamics probed by anisotropic magnetoresistance

H. W. Schumacher, S. Serrano-Guisan, K. Rott, and G. Reiss

Appl. Phys. Lett. 90, 042504 (2007); http://dx.doi.org/10.1063/1.2433759 (3 pages) | Cited 4 times

Online Publication Date: 24 January 2007

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The authors use time resolved measurements of the anisotropic magnetoresistance (AMR) to study ultrafast magnetization dynamics of microstructured disks of Permalloy. The devices show an AMR of the order of 0.25% revealing the characteristic cos2 angular dependence. From the time resolved AMR the authors derive the in plane angular excursion of the magnetization with angular resolution down to 1°. From the decay of the homogeneous precession the authors derive a Gilbert damping parameter of 0.008±0.001. This technique can be applied to study magnetization precession and damping in individual micropatterned devices of a wide variety of magnetic thin film and multilayer materials.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.47.Np Metals and alloys

Electronic structure and magnetism in compressed 3d transition metals

Valentin Iota, Jae-Hyun Park Klepeis, Choong-Shik Yoo, Jonathan Lang, Daniel Haskel, and George Srajer

Appl. Phys. Lett. 90, 042505 (2007); http://dx.doi.org/10.1063/1.2434184 (3 pages) | Cited 21 times

Online Publication Date: 24 January 2007

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The authors present a systematic study of high-pressure effects on electronic structure and magnetism in 3d transition metals (Fe, Co, and Ni) based on x-ray magnetic circular dichroism measurements. The data show that the net magnetic moment in Fe vanishes above 18 GPa upon the transition to hcp Fe, while both cobalt and nickel remain ferromagnetic to well over 100 GPa. The authors estimate the total disappearance of moment in hcp Co at around 150 GPa and predict a nonmagnetic Ni phase above 250 GPa. The present data suggest that the suppression of ferromagnetism in Fe, Co, and Ni is due to pressure-induced broadening of the 3d valence bands.
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71.20.Be Transition metals and alloys
75.50.Bb Fe and its alloys
75.50.Cc Other ferromagnetic metals and alloys
78.20.Ls Magneto-optical effects
75.30.Cr Saturation moments and magnetic susceptibilities
62.50.-p High-pressure effects in solids and liquids

Magnetostatic interactions in patterned CoPt films embedded in a permalloy matrix

S. Schnittger, S. Dreyer, Ch. Jooss, S. Sievers, and U. Siegner

Appl. Phys. Lett. 90, 042506 (2007); http://dx.doi.org/10.1063/1.2435592 (3 pages) | Cited 4 times

Online Publication Date: 24 January 2007

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In order to study magnetostatic interactions in magnetic arrays, a two-dimensional pattern of hard magnetic (001) L10 CoPt squares embedded into a permalloy matrix was fabricated. The structural and magnetic properties of these arrays were characterized by magneto-optical measurements, atomic force and magnetic force microscopies. The hard magnetic squares are not exchange coupled to the soft magnet, yet a magnetostatic coupling was observed. This coupling modifies the domain structure of the permalloy matrix. In periodic arrays of embedded CoPt squares, the stray field interaction induces a long-range ordered domain pattern in the soft magnetic matrix and short-range correlations of edge domains in adjacent CoPt squares.
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75.60.Ch Domain walls and domain structure
75.50.Ww Permanent magnets
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
78.20.Ls Magneto-optical effects
75.50.Cc Other ferromagnetic metals and alloys
81.05.Zx New materials: theory, design, and fabrication

Low-field inverse magnetocaloric effect in Ni50−xMn39+xSn11 Heusler alloys

Z. D. Han, D. H. Wang, C. L. Zhang, H. C. Xuan, B. X. Gu, and Y. W. Du

Appl. Phys. Lett. 90, 042507 (2007); http://dx.doi.org/10.1063/1.2435593 (3 pages) | Cited 75 times

Online Publication Date: 24 January 2007

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The low-field magnetic entropy changes in Ni50−xMn39+xSn11 alloys (x = 5, 6, and 7) were investigated. The martensitic transition shifts to lower temperature with the increase of Mn concentration. Under an applied magnetic field of 10 kOe, the magnetic entropy changes are 6.8, 10.1, and 10.4 J/kg K, for x = 5, 6, and 7, respectively. The large entropy change in Ni50−xMn39+xSn11 can be attributed to the sharp magnetization change associated with the martensitic transition from a ferromagnetic parent phase to a weak-magnetic martensitic phase. The large low-field magnetic entropy change and low cost suggest Ni50−xMn39+xSn11 alloy as the promising magnetic refrigerant.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Cc Other ferromagnetic metals and alloys
81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions

High coercivity L10 FePt films with perpendicular anisotropy deposited on glass substrate at reduced temperature

J. S. Chen, B. C. Lim, J. F. Hu, Y. K. Lim, B. Liu, and G. M. Chow

Appl. Phys. Lett. 90, 042508 (2007); http://dx.doi.org/10.1063/1.2430910 (3 pages) | Cited 29 times

Online Publication Date: 25 January 2007

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The microstructures and magnetic properties of FePt films grown at 350 °C on glass substrates with MgO (200) intermediate layer and CrRu (200) underlayer were investigated. The film with 1 nm MgO intermediate layer showed higher degree of chemical ordering than that with 4 nm MgO layer due to the compression of the lattice constant of 1 nm MgO intermediate layer along the [100] direction. Isolated FePt particles were formed when nominal thickness of FePt was 4 nm. The room temperature coercivity of isolated FePt particles with 1 nm MgO intermediate layer was as high as 12 kOe, significantly larger than that with 4 nm MgO intermediate layer (6.3 kOe).
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75.30.Gw Magnetic anisotropy
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.55.-a Thin film structure and morphology

Ion irradiation and thermally induced mixing of CoCrPt/Cr multilayered films

M. T. Georgieva, P. J. Grundy, and N. D. Telling

Appl. Phys. Lett. 90, 042509 (2007); http://dx.doi.org/10.1063/1.2432256 (3 pages) | Cited 3 times

Online Publication Date: 26 January 2007

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A set of CoCrPt/Cr multilayered films with variable layer thicknesses has been used in an investigation of interlayer mixing and “patterning” of samples with relatively high coercivity and in-plane magnetization. The multilayers with the highest coercivities were irradiated with different doses of Ar++ ions in order to intermix the Cr and CoCrPt layers and push the CoCrPt stoichiometry into the nonmagnetic region of the phase diagram. Samples were also irradiated through a Ni-grating mask to obtain patterning by adjacent magnetic and nonmagnetic regions of the film. Thermal annealing experiments mirrored the change in magnetic properties of the irradiated samples.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Vv High coercivity materials
68.65.Ac Multilayers
61.80.Jh Ion radiation effects

Giant magnetocaloric effect in ε-(Mn0.83Fe0.17)3.25Ge antiferromagnet

J. Du, W. B. Cui, Q. Zhang, S. Ma, D. K. Xiong, and Z. D. Zhang

Appl. Phys. Lett. 90, 042510 (2007); http://dx.doi.org/10.1063/1.2432274 (3 pages) | Cited 22 times

Online Publication Date: 26 January 2007

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The magnetic phase transition and magnetocaloric effect are investigated on ε-(Mn0.83Fe0.17)3.25Ge compound. A large positive magnetic entropy change ΔSM is observed, which is accompanied with a field-induced metamagnetic transition from a collinear to a triangular antiferromagnetic configuration in this antiferromagnetic compound. The maximum value of ΔSM is 11.6 J/kg K at 93 K for a magnetic field change of 7 T. The study on systems with antiferromagnetic phases may open an important field in searching new materials for magnetic refrigeration.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Gw Magnetic anisotropy
75.50.Ee Antiferromagnetics
65.40.G- Other thermodynamical quantities

Magnetic studies of GaN nanoceramics

A. J. Zaleski, M. Nyk, and W. Strek

Appl. Phys. Lett. 90, 042511 (2007); http://dx.doi.org/10.1063/1.2432275 (3 pages) | Cited 2 times

Online Publication Date: 26 January 2007

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The synthesis, morphology, and magnetization measurements of GaN nanoceramics obtained under high pressure are reported. In particular, the effect of grain size on magnetic properties of GaN nanopowders and nanoceramics was investigated. It was found that for the GaN nanoceramic characterized by the stronger deformation of nanocrystalline grains, the diamagnetic signal changes with external magnetic field similarly to the Meissner effect in superconductors.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.20.Ck Nonmetals
81.05.Ea III-V semiconductors
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
62.25.-g Mechanical properties of nanoscale systems
81.40.Lm Deformation, plasticity, and creep

Self-generated in-plane superlattice in relaxed epitaxial La0.67Sr0.33MnO3 films

T. F. Zhou, G. Li, X. G. Li, S. W. Jin, and W. B. Wu

Appl. Phys. Lett. 90, 042512 (2007); http://dx.doi.org/10.1063/1.2432292 (3 pages) | Cited 5 times

Online Publication Date: 26 January 2007

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The strain relaxation and its effect on the in-plane superlattice formation of epitaxial La0.67Sr0.33MnO3 (LSMO) thin films on the (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) [LSAT (001)] substrates were investigated as a function of film thickness by x-ray diffraction. Rocking curves and reciprocal space mappings around (002) and (103) reflections reveal that the film with a thickness above 27 nm is almost fully relaxed and has a modulated superlattice structure. The recovery of the pseudocubic angle of LSMO resulting from the relaxation of the shear strain introduced by the growth of rhombohedral LSMO on cubic LSAT was suggested to be the origin of the superlattice structure.
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68.65.Cd Superlattices
68.55.-a Thin film structure and morphology
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Second harmonic generation and ferroelectric phase transitions in thick and ultrathin Pb0.35Sr0.65TiO3 films on (001) MgO substrates

S. W. Liu, J. Chakhalian, Min Xiao, and C. L. Chen

Appl. Phys. Lett. 90, 042901 (2007); http://dx.doi.org/10.1063/1.2433023 (3 pages) | Cited 12 times

Online Publication Date: 22 January 2007

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Second harmonic generation of a 16-nm-thick ultrathin Pb0.35Sr0.65TiO3 film and a 243-nm-thick Pb0.35Sr0.65TiO3 film grown on (001) MgO substrates by pulsed laser deposition is investigated. It is concluded that in the ultrathin film the ferroelectric phase is still present and the diffuse phase transition is absent. In contrast, the thick film exhibits a pronounced diffuse phase transition. Theoretical analysis based on the polarization diagrams shows that the compensated c-domain fraction is dominant in both films whereas the nonlinear susceptibility of the ultrathin film has a different tensor property from the thick film.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
77.80.B- Phase transitions and Curie point
77.22.Ej Polarization and depolarization
77.55.-g Dielectric thin films

Modeling of imprint in hysteresis loop of ferroelectric thin films with top and bottom interface layers

Z. Ye, M. H. Tang, Y. C. Zhou, X. J. Zheng, C. P. Cheng, Z. S. Hu, and H. P. Hu

Appl. Phys. Lett. 90, 042902 (2007); http://dx.doi.org/10.1063/1.2433026 (3 pages) | Cited 13 times

Online Publication Date: 22 January 2007

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The imprint of a ferroelectric thin film capacitor is studied using an improved model consisting of two nonswitching thin interface layers near the top and bottom electrodes. The difference in electrical conductivity between the two interface layers induces voltage offset and deformation behaviors in hysteresis loops. Size dependence of shift effect of Bi4−xNdxTi3O12 thin film is explained qualitatively by taking into account the thickness ratio of the interface layer and the bulk film. Various shifts and anamorphic shapes with different electrodes and processes have been effectively reproduced through changing the layer conductivities. The simulated shifted hysteresis loops agree well with the experiment. Theoretical prediction based on this approach may provide a method to reduce imprint failure.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.32.Tt Capacitors

Structures and dielectric properties of Bi1.5Zn1.0Nb1.5−xTixO7 (x = 0, 0.05, and 0.10) thin films

Shan-Tao Zhang, Yi-Zhang, Ming-Hui Lu, Yan-Feng Chen, and Zhi-Guo Liu

Appl. Phys. Lett. 90, 042903 (2007); http://dx.doi.org/10.1063/1.2433762 (3 pages) | Cited 10 times

Online Publication Date: 22 January 2007

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B-site Ti-substituted Bi1.5Zn1.0Nb1.5O7 (Bi1.5Zn1.0Nb1.5−xTixO7, x = 0, 0.05, and 0.10) thin films have been fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. The x-ray diffraction and scanning electron microscopy measurements show that the films have a single phase and are well crystallized and homogeneous. Dielectric properties are investigated as function of temperature and frequency. It is found that the Ti substitution increases the dielectric constant. At 10 kHz, the room temperature dielectric constant and loss tangent (ε, tan δ) are (163, 0.006), (182, 0.014), (197, 0.010) for the films with x = 0, 0.05, and 0.10, respectively. In a wide temperature and frequency range (−100 °C ∼ 50 °C, 1 kHz ∼ 1 MHz), the dielectric constant is almost constant. However, below −100 °C, a dielectric relaxation depending on Ti content is observed. The relationship between structure and property of this thin film system is discussed.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
77.22.Gm Dielectric loss and relaxation

Wavelength dependence of light-induced domain nucleation in MgO-doped congruent LiNbO3 crystal

Ya’nan Zhi, De’an Liu, Weijuan Qu, Zhu Luan, and Liren Liu

Appl. Phys. Lett. 90, 042904 (2007); http://dx.doi.org/10.1063/1.2434151 (3 pages) | Cited 7 times

Online Publication Date: 22 January 2007

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Within the wavelength range from 351 to 799 nm, the different reductions of nucleation field induced by the focused continuous laser irradiation are achieved in the 5 mol % MgO-doped congruent LiNbO3 crystals. The reduction proportion increases exponentially with decreasing irradiation wavelength and decreases exponentially with increasing irradiation wavelength. At one given wavelength, the reduction proportion increases exponentially with increasing irradiation intensity. An assumption is proposed that the reduction of nucleation field is directly related to the defect structure of crystal lattice generated by the complex coaction of incident irradiation field and external electric field.
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68.55.A- Nucleation and growth
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.72.-y Defects and impurities in crystals; microstructure

Fabrication and electrical properties of (111) textured (Ba0.6Sr0.4)TiO3 film on platinized Si substrate

Yi Wang, Baoting Liu, Feng Wei, Zhimin Yang, and Jun Du

Appl. Phys. Lett. 90, 042905 (2007); http://dx.doi.org/10.1063/1.2431708 (3 pages) | Cited 8 times

Online Publication Date: 23 January 2007

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The authors report the fabrication of (Ba0.6Sr0.4)TiO3 (BST) film on Pt/Si(001) substrate without Ti adhesion layer by magnetron sputtering. X-ray diffraction technique is used to characterize the orientation and phase purity of BST/Pt heterostructure. It is found that both BST and Pt films are (111) textured. The (111) BST films are observed to have high tunability of 49.4%; the dielectric constant and dielectric loss of the BST film are about 682 and 0.015, respectively. The leakage current density of BST film agrees well with the space-charge-limited current theory at room temperature and is only 3.90×10−8 A/cm2 at 455 kV/cm.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.22.Jp Dielectric breakdown and space-charge effects
68.55.-a Thin film structure and morphology

Charging phenomena in pentacene-gold nanoparticle memory device

W. L. Leong, P. S. Lee, S. G. Mhaisalkar, T. P. Chen, and A. Dodabalapur

Appl. Phys. Lett. 90, 042906 (2007); http://dx.doi.org/10.1063/1.2435598 (3 pages) | Cited 62 times

Online Publication Date: 23 January 2007

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The authors demonstrate a new organic memory system, using pentacene as the active semiconductor layer and citrate-stabilized gold (Au) nanoparticles as charge storage elements. A pronounced clockwise capacitance-voltage (C-V) hysteresis is observed with a memory window of 1.25–2.05 V achievable under 5–10 V programing range. Similar clockwise C-V hysteresis window and an almost constant full width at half maximum of the conductance peaks in conductance-voltage (G-V) characteristics, obtained in the frequency range of 50 kHz–1 MHz, indicated that positive charge trapping/detrapping originated mainly from the Au nanoparticles.
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85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Resonance Raman scattering of relaxors PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3

B. Mihailova, M. Bastjan, B. Schulz, M. Rübhausen, M. Gospodinov, R. Stosch, B. Güttler, T. Malcherek, and U. Bismayer

Appl. Phys. Lett. 90, 042907 (2007); http://dx.doi.org/10.1063/1.2433763 (3 pages) | Cited 2 times

Online Publication Date: 23 January 2007

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Relaxor PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3 single crystals are studied at room temperature using resonance Raman scattering. It is shown that the phonon modes associated with O localized BO6 vibrations in ferroic clusters strongly resonate in the vicinity of the maximum of the optical dielectric response function at 3.71 eV. Resonance Raman spectroscopy can be used to estimate the fraction and the average size of polar nanoclusters in the relaxor state.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
78.30.Hv Other nonmetallic inorganics
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Room temperature multiferroic properties of single-phase (Bi0.9La0.1)FeO3–Ba(Fe0.5Nb0.5)O3 solid solution ceramics

Hanjong Paik, Hosung Hwang, Kwangsoo No, Seunghwa Kwon, and David P. Cann

Appl. Phys. Lett. 90, 042908 (2007); http://dx.doi.org/10.1063/1.2434182 (3 pages) | Cited 13 times

Online Publication Date: 24 January 2007

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The crystal structure and multiferroic properties of single-phase (Bi0.9La0.1)FeO3–Ba(Fe0.5Nb0.5)O3 ceramics were investigated. The rhombohedral-type structure of 1.0(Bi0.9La0.1)FeO3) was transformed to a monoclinic-type structure for the 0.5(Bi0.9La0.1)FeO3–0.5Ba(Fe0.5Nb0.5)O3) composition. It shows the coexistence of ferroelectricity and magnetism at room temperature, represented by a high dielectric constant with ferroelectric hysteresis and clear magnetic hysteresis behavior. The authors propose that the solid solution of A and B site cations according to their ionic radii and valence state stabilized the spontaneous polarization and magnetization at room temperature.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
75.50.Dd Nonmetallic ferromagnetic materials
61.66.Fn Inorganic compounds
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization

Acoustic Bragg mirrors and cavities made using piezoelectric oxides

A. Soukiassian, W. Tian, D. A. Tenne, X. X. Xi, D. G. Schlom, N. D. Lanzillotti-Kimura, A. Bruchhausen, A. Fainstein, H. P. Sun, X. Q. Pan, A. Cros, and A. Cantarero

Appl. Phys. Lett. 90, 042909 (2007); http://dx.doi.org/10.1063/1.2432246 (3 pages) | Cited 20 times

Online Publication Date: 24 January 2007

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The concept and design of acoustic Bragg mirrors and cavities made of multilayers of piezoelectric oxides with superior acoustic performance and potential applications in electronic and optical terahertz modulators are described. With these applications in mind the authors have grown phonon mirrors consisting of BaTiO3/SrTiO3 superlattices on SrTiO3 substrates by reactive molecular-beam epitaxy and investigated their properties. Characterization of the superlattices by x-ray diffraction and high-resolution transmission electron microscopy reveals high structural quality with nearly atomically abrupt interfaces. The authors have observed folded acoustic phonons at the expected frequencies using uv Raman spectroscopy.
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42.79.Jq Acousto-optical devices
42.79.Bh Lenses, prisms and mirrors
68.65.Cd Superlattices
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.30.Hv Other nonmetallic inorganics
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Low temperature growth of crystalline magnesium oxide on hexagonal silicon carbide (0001) by molecular beam epitaxy

T. L. Goodrich, J. Parisi, Z. Cai, and K. S. Ziemer

Appl. Phys. Lett. 90, 042910 (2007); http://dx.doi.org/10.1063/1.2436636 (3 pages) | Cited 14 times

Online Publication Date: 25 January 2007

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Magnesium oxide (111) was grown epitaxially on hexagonal silicon carbide (6H-SiC) (0001) substrates at low temperatures by molecular beam epitaxy and a remote oxygen plasma source. The films were characterized by reflection high-energy electron diffraction, Auger electron spectroscopy, x-ray photoelectron spectroscopy, and atomic force microscopy. Crystal structure, morphology, and growth rate of the magnesium oxide (MgO) films were found to be dependent on the magnesium flux, indicating a magnesium adsorption controlled growth mechanism. The single crystalline MgO thin films had an epitaxial relationship where MgO (111)‖6H-SiC (0001) and were stable in both air and 10−9 Torr up to 1023 K.
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.-j Plasma applications
68.37.Xy Scanning Auger microscopy, photoelectron microscopy
68.43.Mn Adsorption kinetics

Phase transitional behavior and electrical properties of lead-free (K0.44Na0.52Li0.04)(Nb0.96−xTaxSb0.04)O3 piezoelectric ceramics

Zupei Yang, Yunfei Chang, and Lingling Wei

Appl. Phys. Lett. 90, 042911 (2007); http://dx.doi.org/10.1063/1.2436648 (3 pages) | Cited 40 times

Online Publication Date: 25 January 2007

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Lead-free (K0.44Na0.52Li0.04)(Nb0.96−xTaxSb0.04)O3 piezoelectric ceramics have been synthesized by conventional solid state sintering process. Two morphotropic phase boundaries (MPBs) respectively corresponding to the orthorhombic to tetragonal and tetragonal to pseudocubic phases are observed with increasing x. The ceramics with x = 0.20 between the two MPBs show significantly enhanced electrical properties, which are as follows: piezoelectric constant d33 = 252 pC/N, planar coupling coefficient kp = 0.42, dielectric constant εr = 1503, and dielectric loss tan δ = 0.025, and they show good stability. Lead-free superthin buzzer disks have been prepared by using piezoceramic membrane with x = 0.20. (K0.44Na0.52Li0.04)(Nb0.96−xTaxSb0.04)O3 ceramics are very promising as lead-free replacements for lead zirconate titanate.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
64.70.K- Solid-solid transitions
77.65.Bn Piezoelectric and electrostrictive constants
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Effect of vanadium content on remanent polarization in bismuth titanate thin films prepared by liquid source misted chemical deposition

Tai Suk Kim, Ki Woong Kim, Min Ku Jeon, Chang Hwa Jung, and Seong Ihl Woo

Appl. Phys. Lett. 90, 042912 (2007); http://dx.doi.org/10.1063/1.2432226 (3 pages) | Cited 3 times

Online Publication Date: 26 January 2007

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Bi4−x/3Ti3−xVxO12 (BTV) ferroelectric thin films were fabricated by liquid source misted chemical deposition. The substitution of vanadium for titanium site changed the crystalline orientation and surface morphology of the thin film, which in turn influenced the remanent polarization (Pr). 2Pr of BTV thin film increased with increase of vanadium content and reached a maximum value (21.5 μC/cm2) at x = 0.03, as this corresponded with the largest degree of a-axis orientation. However, at 0.05 ⩽ x ⩽ 0.09, 2Pr reduced with decrease in the degree of a-axis orientation. These results indicate that the Pr of the films is dependent on the degree of a-axis orientation.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.-a Thin film structure and morphology

Dielectric and ferroelectric properties of BaTiO3–(Na1/4Bi3/4)(Mg1/4Ti3/4)O3 ceramics

Xiaoli Wang and Wenjuan Cao

Appl. Phys. Lett. 90, 042913 (2007); http://dx.doi.org/10.1063/1.2432229 (3 pages) | Cited 7 times

Online Publication Date: 26 January 2007

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Perovskite ceramics (1−x)BaTiO3–x(Na1/4Bi3/4)(Mg1/4Ti3/4)O3 (x ⩽ 0.10) were prepared using solid-state reaction. The permittivity peak of the compositions x = 0.08 and 0.10 is saddle backed. The high turning temperature fixes at ∼ 400 K and is the Burns temperature TB of the samples. The low turning point decreases with increasing content of (Na1/4Bi3/4)(Mg1/4Ti3/4)O3 and is associated with transformation between domains and polar nanoregions. The P-E relationship indicates that the permittivity in the saddle-backed region for composition x = 0.10 is quasilinear when E<2 MV/m. The behavior suggests a possible way for developing linear dielectrics with very high permittivity.
Show PACS
77.80.B- Phase transitions and Curie point
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
61.66.Fn Inorganic compounds
64.70.K- Solid-solid transitions
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