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10 Dec 2007

Volume 91, Issue 24, Articles (24xxxx)

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Appl. Phys. Lett. 91, 241101 (2007); http://dx.doi.org/10.1063/1.2821382 (3 pages)

S. N. Goda, S. Sensarn, M. Y. Shverdin, and G. Y. Yin
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Monolithic integration of InP based heterostructures on silicon using crystalline Gd2O3 buffers

G. Saint-Girons, P. Regreny, L. Largeau, G. Patriarche, and G. Hollinger

Appl. Phys. Lett. 91, 241912 (2007); http://dx.doi.org/10.1063/1.2824466 (3 pages) | Cited 25 times

Online Publication Date: 14 December 2007

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An original approach of monolithic integration of InP based heterostructures on silicon is proposed based on the peculiar properties of the heterointerface between InP and crystalline Gd2O3. When grown on a crystalline Gd2O3/Si(111) buffer, InP takes its bulk lattice parameter as soon as the growth begins, and the lattice mismatch (7.9%) is fully accommodated by the formation of a misfit dislocation network at the InP/Gd2O3 heterointerface. This plastic compliant effect allows the monolithic growth of good quality InAsP/InP heterostructures on Si, as attested by room-temperature photoluminescence experiments.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.66.Fn Inorganic compounds
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
78.55.Cr III-V semiconductors

On incompressibility of a matrix in naturally occurring composites

Larissa Gorbatikh and Pawan Pingle

Appl. Phys. Lett. 91, 241913 (2007); http://dx.doi.org/10.1063/1.2824467 (3 pages)

Online Publication Date: 14 December 2007

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The work illustrates that a soft matrix, which has the Poisson ratio close to 0.5 and is reinforced with a rigid-line inclusion, possesses an interesting behavior at the inclusion/matrix interface. It experiences a hydrostatic stress state and behaves as an incompressible fluid under longitudinal and transverse loads. The stress singularities are eliminated ahead of the inclusion tips, and when interface defects are formed, their effect on the composite compliance is minimal. These observations have far reaching applications when one is interested in mechanisms of multifunctional property improvement of composites (such as toughness and stiffness) learned from naturally occurring composites.
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61.72.Qq Microscopic defects (voids, inclusions, etc.)
62.20.D- Elasticity

Surface hardness enhancement in sp3-bonded carbon doped SiC nanocomposite films

Xiaodong He, Jian Yi, Yue Sun, Ping Xiao, and Xiaofeng Zhao

Appl. Phys. Lett. 91, 241914 (2007); http://dx.doi.org/10.1063/1.2824811 (3 pages) | Cited 1 time

Online Publication Date: 14 December 2007

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The sp3-bonded carbon/SiC composite films have been produced from electron beam-physical vapor deposition of SiC materials. The hardness of such films, measured using Hysitron indentation, reaches 50 GPa, which is significantly higher than the hardness of SiC (28 GPa). It appears that the superhardness of the thin films is due to the formation of nanocrystalline SiC/diamondlike carbon composites.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
61.46.-w Structure of nanoscale materials
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness

Strain influence on valence-band ordering and excitons in ZnO: An ab initio study

A. Schleife, C. Rödl, F. Fuchs, J. Furthmüller, and F. Bechstedt

Appl. Phys. Lett. 91, 241915 (2007); http://dx.doi.org/10.1063/1.2825277 (3 pages) | Cited 21 times

Online Publication Date: 14 December 2007

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Modern parameter-free methods to treat single- and two-particle electronic excitations are applied to compute the band structure and the lowest optical transitions of wurtzite ZnO under biaxial strain. The calculations are based on density functional theory with a spatially nonlocal exchange and correlation functional and include spin-orbit interaction. Quasiparticle shifts and excitonic effects are computed. In addition to the band parameters, also their dependence on biaxial strain and the ordering of the A, B, and C excitons are investigated. While the crystal-field splitting is very sensitive to strain, the spin-orbit splittings and the exciton binding energies remain unaffected.
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71.20.Nr Semiconductor compounds
71.35.-y Excitons and related phenomena
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.70.Ch Crystal and ligand fields
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Tailoring magnetic and magnetocaloric properties of martensitic transitions in ferromagnetic Heusler alloys

Seda Aksoy, Thorsten Krenke, Mehmet Acet, Eberhard F. Wassermann, Xavier Moya, Lluís Mañosa, and Antoni Planes

Appl. Phys. Lett. 91, 241916 (2007); http://dx.doi.org/10.1063/1.2825283 (3 pages) | Cited 38 times

Online Publication Date: 14 December 2007

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Ni50Mn34In16 undergoes a martensitic transformation around 250 K and exhibits a field induced reverse martensitic transformation and substantial magnetocaloric effects. We substitute small amounts Ga for In, which are isoelectronic, to carry these technically important properties to close to room temperature by shifting the martensitic transformation temperature.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Cc Other ferromagnetic metals and alloys
81.30.Kf Martensitic transformations
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Effect of optical lithography patterning on the crystalline structure of tunnel junctions

C. Mocuta, A. Barbier, A. V. Ramos, M.-J. Guittet, J.-B. Moussy, S. Stanescu, R. Mattana, C. Deranlot, and F. Petroff

Appl. Phys. Lett. 91, 241917 (2007); http://dx.doi.org/10.1063/1.2824858 (3 pages) | Cited 1 time

Online Publication Date: 14 December 2007

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The crystalline structure of metal-oxide-based magnetic tunnel junctions patterned by optical lithography was resolved locally using a microfocused x-ray spot. We evidence several micron-sized lithography-induced distortion effects on the crystalline structure of the layers near the edges of the junction. The distortions translate into tilts (up to 1°) of the crystalline planes in the vicinity of the edges and propagate toward the center of the junction. They are attributed to the release of the elastic strain in the layers during the lithographical process. For the smallest junctions, size effects limiting the amplitude of the tilt are also evidenced.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Microphotoluminescence evaluation of local strain for freestanding Si membranes with SiN deposition

Dong Wang, Hiroshi Nakashima, Jun Morioka, and Tokuhide Kitamura

Appl. Phys. Lett. 91, 241918 (2007); http://dx.doi.org/10.1063/1.2825271 (3 pages) | Cited 4 times

Online Publication Date: 14 December 2007

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Microphotoluminescence (PL) was used to evaluate the local strain for freestanding Si membranes, which were fabricated by the mesa etching of Si on insulator followed by etching of the buried oxide. Compressive strain in the membranes was induced by SiN deposition using low-pressure chemical vapor deposition. Strain-induced band gap narrowing was directly observed by identifying the PL peak of the free exciton band-band transition in membranes, from which the strain ratio was estimated for each sample. Strain was reasonably dependent on the sample parameters, which implies that this measurement gives valid results.
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68.60.Bs Mechanical and acoustical properties
78.66.-w Optical properties of specific thin films
78.55.-m Photoluminescence, properties and materials
73.20.At Surface states, band structure, electron density of states
71.35.-y Excitons and related phenomena
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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Interfacial characteristics and band alignments for ZrO2 gate dielectric on Si passivated p-GaAs substrate

Goutam Kumar Dalapati, Aaditya Sridhara, Andrew See Weng Wong, Ching Kean Chia, Sung Joo Lee, and Dongzhi Chi

Appl. Phys. Lett. 91, 242101 (2007); http://dx.doi.org/10.1063/1.2822422 (3 pages) | Cited 19 times

Online Publication Date: 10 December 2007

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The interfacial characteristics and band alignments of high-k ZrO2 on p-GaAs have been investigated by using x-ray photoelectron spectroscopy and electrical measurements. It has been demonstrated that the presence of Si interfacial passivation layer (IPL) improves GaAs metal-oxide-semiconductor device characteristics such as interface state density, accumulation capacitance, and hysteresis. It is also found that Si IPL can reduce interfacial GaAs-oxide formation and increases effective valence-band offset at ZrO2/p-GaAs interface. The effective valence-band offsets of ZrO2/p-GaAs and ZrO2/Si/p-GaAs interfaces are determined to be 2.7 and 2.84 eV, while the effective conduction-band offsets are found to be 1.67 and 1.53 eV, respectively.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.65.Rv Passivation
85.30.Tv Field effect devices
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Enhancement of Seebeck coefficient for SrO(SrTiO3)2 by Sm substitution: Crystal symmetry restoration of distorted TiO6 octahedra

Yifeng Wang, Kyu Hyoung Lee, Hideki Hyuga, Hideki Kita, Katsuhiko Inaba, Hiromichi Ohta, and Kunihito Koumoto

Appl. Phys. Lett. 91, 242102 (2007); http://dx.doi.org/10.1063/1.2820447 (3 pages) | Cited 5 times

Online Publication Date: 10 December 2007

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We found that Sm3+ substitution in SrO(SrTiO3)2 is effective in improving the Seebeck coefficient (S). The ∣S∣ value increases notably with temperature, benefiting from an enhancement of the density of states (DOS) effective mass md* from ∼ 3m0 (300 K) to  ∼ 7.5m0 (1000 K), due to an improvement of the local symmetry of TiO6 octahedra, enhancing the degeneracy in the Ti 3d orbitals, which form the conduction band (CB), and also to an accompanying lattice expansion, which gives rise to a higher DOS at the bottom of the CB and, consequently, a larger md*.
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73.50.Lw Thermoelectric effects
73.61.Le Other inorganic semiconductors
71.20.Ps Other inorganic compounds
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.20.At Surface states, band structure, electron density of states
72.20.Pa Thermoelectric and thermomagnetic effects

Trap-controlled hole transport in small molecule organic semiconductors

Arne Fleissner, Hanna Schmid, Christian Melzer, and Heinz von Seggern

Appl. Phys. Lett. 91, 242103 (2007); http://dx.doi.org/10.1063/1.2820448 (3 pages) | Cited 8 times

Online Publication Date: 11 December 2007

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The influence of trap concentration on hole transport is investigated by an optical time-of-flight method for the amorphous small molecule organic semiconductor N,N′-bis(1-naphtyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamin (α-NPD) doped with neutral hole traps by codeposition of 4,4′,4″-tris-[N-(1-naphtyl)-N-(phenylamino)]-triphenylamine (1-NaphDATA). α-NPD doped with 120 ppm 1-NaphDATA exhibits nondispersive hole transport like undoped α-NPD, but trap-controlled with reduced mobility. The trap depth derived from the mobility decrease coincides with the ionization potential difference of α-NPD and 1-NaphDATA. The transition to dispersive transport for increasing trap concentration to 1160 ppm is explained by an energetic relaxation of optically generated charge carriers within a density of states broadened by traps.
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72.20.Fr Low-field transport and mobility; piezoresistance
81.05.Hd Other semiconductors
72.80.Le Polymers; organic compounds (including organic semiconductors)

Giant tunnel magnetoresistance in codeposited fullerene-cobalt films in the low bias-voltage regime

Seiji Sakai, Isamu Sugai, Seiji Mitani, Koki Takanashi, Yoshihiro Matsumoto, Hiroshi Naramoto, Pavel V. Avramov, Satoru Okayasu, and Yoshihito Maeda

Appl. Phys. Lett. 91, 242104 (2007); http://dx.doi.org/10.1063/1.2822397 (3 pages) | Cited 16 times

Online Publication Date: 12 December 2007

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Magnetotransport properties in the low bias-voltage regime were investigated for codeposited C60–Co films. A giant tunnel magnetoresistance (MR) ratio (ΔR/Rmax) of 80%, which is the highest in ferromagnetic metal/organic molecule systems, was found at low temperatures. The observed bias-voltage dependence of the MR ratio is expressed by an unusual exponential form, suggesting that the MR ratio of nearly 100% can be realized in the low bias-voltage limit.
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75.50.Cc Other ferromagnetic metals and alloys
75.50.Dd Nonmetallic ferromagnetic materials
81.05.ub Fullerenes and related materials
75.47.De Giant magnetoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Effects of strain and interface on work function of a Nb–W metal gate system

H. R. Gong, Yoshio Nishi, and Kyeongjae Cho

Appl. Phys. Lett. 91, 242105 (2007); http://dx.doi.org/10.1063/1.2821225 (3 pages) | Cited 10 times

Online Publication Date: 12 December 2007

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First principles calculation reveals that the compressed (tensile) strain increases (decreases) the work function of Nb and W (110) surfaces, and that such a work function change is due to the combined effects of the surface dipole and bulk electronic structure toward the same direction. Calculation also shows that the interface dipole is formed in the Nb–W interface due to an unequal loss of the electrons from Nb and W interface atoms, and that the formation of the Nb–W interface is energetically favorable with negative interface energy, implying a tendency of interface interdiffusion of Nb and W atoms.
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73.40.Cg Contact resistance, contact potential
73.30.+y Surface double layers, Schottky barriers, and work functions
73.20.At Surface states, band structure, electron density of states
68.35.Md Surface thermodynamics, surface energies
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Gy Mechanical properties; surface strains

Spin-dependent scattering off neutral antimony donors in 28Si field-effect transistors

C. C. Lo, J. Bokor, T. Schenkel, A. M. Tyryshkin, and S. A. Lyon

Appl. Phys. Lett. 91, 242106 (2007); http://dx.doi.org/10.1063/1.2817966 (3 pages) | Cited 18 times

Online Publication Date: 12 December 2007

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We report measurements of spin-dependent scattering of conduction electrons by neutral donors in accumulation-mode field-effect transistors formed in isotopically enriched silicon. Spin-dependent scattering was detected using electrically detected magnetic resonance where spectra show resonant changes in the source-drain voltage for conduction electrons and electrons bound to donors. We discuss the utilization of spin-dependent scattering for the readout of donor spin states in silicon based quantum computers.
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72.25.-b Spin polarized transport
85.30.Tv Field effect devices
85.75.Hh Spin polarized field effect transistors

Electret mechanism, hysteresis, and ambient performance of sol-gel silica gate dielectrics in pentacene field-effect transistors

T. Cahyadi, H. S. Tan, S. G. Mhaisalkar, P. S. Lee, F. Boey, Z.-K. Chen, C. M. Ng, V. R. Rao, and G. J. Qi

Appl. Phys. Lett. 91, 242107 (2007); http://dx.doi.org/10.1063/1.2821377 (3 pages) | Cited 7 times

Online Publication Date: 12 December 2007

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The electret induced hysteresis was studied in sol-gel silica films that result in higher drain currents and improved device performance in pentacene field-effect transistors. Vacuum and ambient condition studies of the hysteresis behavior and capacitance-voltage characteristics on single layer and varying thicknesses of bilayer dielectrics confirmed that blocking layers of thermal oxide could effectively eliminate the electret induced hysteresis, and that thin (25 nm) sol-gel silica dielectrics enabled elimination of nanopores thus realizing stable device characteristics under ambient conditions.
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85.30.Tv Field effect devices
77.55.-g Dielectric thin films

Schottky barrier height tuning of silicide on Si1−xCx

Mantavya Sinha, Eng Fong Chor, and Chung Foong Tan

Appl. Phys. Lett. 91, 242108 (2007); http://dx.doi.org/10.1063/1.2820386 (3 pages) | Cited 6 times

Online Publication Date: 14 December 2007

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We have demonstrated the tuning of Schottky barrier height (SBH) of nickel silicide on silicon-carbon (Si1−xCx) by varying the carbon mole fraction, x. The SBH (for electron conduction) has been found to decrease with carbon concentration at a rate of ∼ 6.6 meV/ (0.1% carbon). We have achieved ∼ 27 meV drop in SBH with 0.4% carbon incorporation in Si1−xCx and shown that 1.3% carbon could lead to more than 85 meV improvement. Furthermore, our results show an avenue to reduce the SBH of rare earth silicide contacts in n-channel Schottky transistors by fabricating them on Si1−xCx.
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73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.Tv Field effect devices

106 years extrapolated hole storage time in GaSb/AlAs quantum dots

A. Marent, M. Geller, A. Schliwa, D. Feise, K. Pötschke, D. Bimberg, N. Akçay, and N. Öncan

Appl. Phys. Lett. 91, 242109 (2007); http://dx.doi.org/10.1063/1.2824884 (3 pages) | Cited 25 times

Online Publication Date: 14 December 2007

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A thermal activation energy of 710 meV for hole emission from InAs/GaAs quantum dots (QDs) across an Al0.9Ga0.1As barrier is determined by using time-resolved capacitance spectroscopy. A hole storage time of 1.6 s at room temperature is directly measured, being three orders of magnitude longer than a typical dynamic random access memory (DRAM) refresh time. The dependence of the hole storage time in different III–V QDs on their localization energy is determined and the localization energies in GaSb-based QDs are calculated using eight-band k⋅p theory. A storage time of about 106 years in GaSb/AlAs QDs is extrapolated, sufficient for a QD-based nonvolatile (flash) memory.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
73.63.Kv Quantum dots
73.61.Ey III-V semiconductors
73.21.La Quantum dots

Percolative effects on noise in pentacene transistors

B. R. Conrad, W. G. Cullen, W. Yan, and E. D. Williams

Appl. Phys. Lett. 91, 242110 (2007); http://dx.doi.org/10.1063/1.2823577 (3 pages) | Cited 11 times

Online Publication Date: 14 December 2007

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Noise in pentacene thin film transistors has been measured as a function of device thickness from well above the effective conduction channel thickness to only two conducting layers. Over the entire thickness range, the spectral noise form is 1/f, and the noise parameter varies inversely with gate voltage, confirming that the noise is due to mobility fluctuations, even in the thinnest films. Hooge’s parameter varies as an inverse power law with conductivity for all film thicknesses. The magnitude and transport characteristics of the spectral noise are well explained in terms of percolative effects arising from the grain boundary structure.
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85.30.Tv Field effect devices

Systematic study on p-type doping control of InN with different Mg concentrations in both In and N polarities

Xinqiang Wang, Song-Bek Che, Yoshihiro Ishitani, and Akihiko Yoshikawa

Appl. Phys. Lett. 91, 242111 (2007); http://dx.doi.org/10.1063/1.2824816 (3 pages) | Cited 27 times

Online Publication Date: 14 December 2007

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p-type conductivity control of In- and N-polar InN layers grown on GaN templates with different Mg concentrations ([Mg]) was systematically investigated by using electrolyte-based capacitance-voltage (ECV) analyses. With increasing [Mg], p-type conduction was confirmed for [Mg]s from ∼ 1018 to  ∼ 3×1019 cm−3. The conduction was reversed to n type at [Mg]s above 1020 cm−3, however, due to overdoping effects introducing shallow donors in InN. Further, it was found that charges at the interface states located within forbidden band of InN greatly affected the ECV measurements resulting in overestimation of net acceptor concentrations, and some calibration was necessary to estimate them.
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73.61.Ey III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.20.At Surface states, band structure, electron density of states
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Spin-torque-driven vortex dynamics in a spin-valve pillar with a perpendicular polarizer

Yaowen Liu, Huan He, and Zongzhi Zhang

Appl. Phys. Lett. 91, 242501 (2007); http://dx.doi.org/10.1063/1.2822436 (3 pages) | Cited 25 times

Online Publication Date: 10 December 2007

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Spin-torque-driven vortex dynamics are studied by micromagnetic modeling in a spin-valve pillar which contains a perpendicular polarizer and a vortex free layer. Two kinds of transient oscillations mediated by the vortex-core motion are observed. The oscillations are treated as the competition among the spin torque, gyroforce, Gilbert damping, and the restoring force, governed by the generalized Thiele equation [ A. A. Thiele, J. Appl. Phys. 45, 377 (1974) ]. The fundamental frequency is dominated by the gyrotropic motion, while the high-frequency oscillation is triggered by the balance of the spin torque and demagnetizing field. The polarity of the vortex core can be switched through a vortex-antivortex pair creation and annihilation process.
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72.25.-b Spin polarized transport
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields

Correlation between photoluminescence and magnetic properties of GaMnN films

N. Nepal, Amr M. Mahros, S. M. Bedair, N. A. El-Masry, and J. M. Zavada

Appl. Phys. Lett. 91, 242502 (2007); http://dx.doi.org/10.1063/1.2823602 (3 pages) | Cited 2 times

Online Publication Date: 10 December 2007

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GaMnN films grown by metal-organic chemical vapor deposition were studied by photoluminescence (PL) spectroscopy and hysteresis measurements. Depending on the growth conditions of these GaMnN films, hysteresis measurements along the easy axis of magnetization show a transformation from magnetic to nonmagnetic behavior. The PL spectra of both magnetic and nonmagnetic GaMnN films exhibited GaN band edge and deep-level impurity transitions at 3.4 and 1.3 eV, respectively. The PL emission intensity of the 1.3 eV emission peak is stronger considerably for magnetic GaMnN films and is believed to be due to the Mn3+ intraband transition.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
75.50.Pp Magnetic semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.05.Ea III-V semiconductors

Room temperature magnetocaloric effect in Ni–Mn–In

P. A. Bhobe, K. R. Priolkar, and A. K. Nigam

Appl. Phys. Lett. 91, 242503 (2007); http://dx.doi.org/10.1063/1.2823601 (3 pages) | Cited 34 times

Online Publication Date: 11 December 2007

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We have studied the effect of magnetic field on a nonstoichiometric Heusler alloy Ni50Mn35In15 that undergoes a martensitic as well as a magnetic transition near room temperature. Temperature dependent magnetization measurements demonstrate the influence of magnetic field on the structural phase transition temperature. From the study of magnetization as a function of applied field, we show the occurrence of inverse-magnetocaloric effect associated with this magneto-structural transition. The magnetic entropy change attains a value as high as 25 J/kg K (at 5 T field) at room temperature as the alloy transforms from the austenitic to martensitic phase with a concomitant magnetic ordering.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.05.Bx Metals, semimetals, and alloys

Effects of Ta seed layer and annealing on magnetoresistance in CoFe/Pd-based pseudo-spin-valves with perpendicular anisotropy

Randall Law, Rachid Sbiaa, Thomas Liew, and Tow Chong Chong

Appl. Phys. Lett. 91, 242504 (2007); http://dx.doi.org/10.1063/1.2824832 (3 pages) | Cited 32 times

Online Publication Date: 12 December 2007

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We have studied the switching characteristics and magnetoresistance of pseudo-spin-valves with perpendicular anisotropy based on CoFe/Pd multilayers. In unpatterned thin films without exchange biasing, a maximum current-in-plane giant magnetoresistance of 7% was achieved, the highest reported to date in perpendicular pseudo-spin-valves. A Ta seed layer and the fcc (111) orientation of Pd was shown to be important in order to achieve good perpendicular anisotropy and sharp switching behavior. The improvement in perpendicular anisotropy and decay in magnetoresistance upon postdeposition annealing have been attributed to the formation of CoPd alloys at the CoFe/Pd interfaces.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Gw Magnetic anisotropy
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Nt Magnetic annealing and temperature-hysteresis effects
75.47.De Giant magnetoresistance

Particular strain relaxation for La0.8Ba0.2MnO3 films on SrTiO3 (100) substrates

Hsiung Chou, C. B. Wu, F. P. Yun, Z. H. Zhang, and W. K. Chu

Appl. Phys. Lett. 91, 242505 (2007); http://dx.doi.org/10.1063/1.2824482 (3 pages) | Cited 2 times

Online Publication Date: 14 December 2007

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A particular two stage strain relaxation phenomenon on La0.8Ba0.2MnO3 thick films has been observed. A fully strained bottom layer near the film/substrate interface consists of a moderate density of dislocations, while a top layer exhibits a high density of dislocations, becoming denser as it nears the surface of the film. This phenomenon can be attributed to the partial diffusion of the substrate element, Sr, into the bottom layer of the film, which reduces its lattice constant, and to the sudden change of the lattice constants at the bottom-top-layer interface due to the stoppage of Sr diffusion.
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68.35.Fx Diffusion; interface formation
61.72.Lk Linear defects: dislocations, disclinations
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Rapid liquid phase sintered Mn doped BiFeO3 ceramics with enhanced polarization and weak magnetization

Manoj Kumar and K. L. Yadav

Appl. Phys. Lett. 91, 242901 (2007); http://dx.doi.org/10.1063/1.2816118 (3 pages) | Cited 27 times

Online Publication Date: 12 December 2007

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Single-phase BiFe1−xMnxO3 multiferroic ceramics have been synthesized by rapid liquid phase sintering method to study the influence of Mn substitution on their crystal structure, dielectric, magnetic, and ferroelectric behaviors. From XRD analysis it is seen that Mn substitution does not affect the crystal structure of the BiFe1−xMnxO3 system. An enhancement in magnetization was observed for BiFe1−xMnxO3 ceramics. However, the ferooelectric hysteresis loops were not really saturated, we observed a spontaneous polarization of 10.23 μC/cm2 under the applied field of 42 kV/cm and remanent polarization of 3.99 μC/cm2 for x = 0.3 ceramic.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.80.Dj Domain structure; hysteresis
61.66.Fn Inorganic compounds

Analysis of relaxor mechanism and structural distortion for SrBi1.6Nd0.4Nb2O9 bismuth-layer-structured ceramics

Lin Sun, Junhao Chu, Chude Feng, and Lidong Chen

Appl. Phys. Lett. 91, 242902 (2007); http://dx.doi.org/10.1063/1.2824383 (3 pages)

Online Publication Date: 13 December 2007

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Show Abstract
The 1/2{h00} and 1/2{hk0} type superlattice reflections in the electron diffraction patterns indicate the presence of ordered polar regions in SrBi1.6Nd0.4Nb2O9. The research of x-ray Rietveld refinement and synchrotron radiation x-ray absorption fine structure spectroscopy determined that Nd3+ replaced Bi3+ in the Bi2O2 layers for SrBi1.6Nd0.4Nb2O9 and the relaxor behavior could be attributed to the disorder of Nd3+ and Bi3+ in the Bi2O2 layers. The tilting angle of NbO6 is obtained by Rietveld refinement method and the refinement result indicates that the substitution of Nd3+ for Bi3+ remarkably decrease the structural distortion, which leads to the lower transition temperature.
Show PACS
77.80.B- Phase transitions and Curie point
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
61.66.Fn Inorganic compounds
78.70.Dm X-ray absorption spectra
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