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27 Mar 2006

Volume 88, Issue 13, Articles (13xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 133105 (2006); http://dx.doi.org/10.1063/1.2189203 (3 pages)

Premila Mohan, Junichi Motohisa, and Takashi Fukui
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X-ray elastic constants for α-Al2O3

D. B. Hovis, A. Reddy, and A. H. Heuer

Appl. Phys. Lett. 88, 131910 (2006); http://dx.doi.org/10.1063/1.2189071 (3 pages) | Cited 6 times

Online Publication Date: 29 March 2006

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It has recently been discovered that there is a long-standing error in the sign of c14 for α-Al2O3—it is +22 rather than −22 GPa. Although c14 is the smallest of the six elastic constants of α-Al2O3 (space group Rmathc), it has a significant effect on the Reuss x-ray elastic constants, particularly for the {02math4} reflection. Measurements using the Advanced Photon Source have confirmed that the sign of c14 must be positive. Use of the wrong sign of c14 can induce errors in excess of 30% in the measured residual stresses of α-Al2O3 scales.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
61.05.cp X-ray diffraction

Strain relief by periodic misfit arrays for low defect density GaSb on GaAs

S. H. Huang, G. Balakrishnan, A. Khoshakhlagh, A. Jallipalli, L. R. Dawson, and D. L. Huffaker

Appl. Phys. Lett. 88, 131911 (2006); http://dx.doi.org/10.1063/1.2172742 (3 pages) | Cited 44 times

Online Publication Date: 30 March 2006

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We demonstrate the growth of a low dislocation density, relaxed GaSb bulk layer on a (001) GaAs substrate. The strain energy generated by the 7.78% lattice mismatch is relieved by a periodic array of 90° misfit dislocations. The misfit array is localized at the GaSb/GaAs interface and has a period of 5.6 nm which is determined by transmission electron microscope images. No threading dislocations are visible. The misfits are identified as 90°, rather than 60°, using Burger’s circuit analysis, and are therefore not associated with generation of threading dislocations. A low dislocation density and planar growth mode is established after only 3 monolayers of GaSb deposition as revealed by reflection high-energy electron diffraction patterns. Calculations corroborate the materials characterization and indicate the strain energy generated by the 7.78% lattice mismatch is almost fully dissipated by the misfit array. The low dislocation density bulk GaSb material on GaAs enabled by this growth mode will lead to new devices, especially in the infrared regime, along with novel integration schemes.
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68.60.Bs Mechanical and acoustical properties
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Lp Transmission electron microscopy (TEM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Ea III-V semiconductors

SnO2 nanoparticles in silica: Nanosized tools for femtosecond-laser machining of refractive index patterns

A. Paleari, E. Franchina, N. Chiodini, A. Lauria, E. Bricchi, and P. G. Kazansky

Appl. Phys. Lett. 88, 131912 (2006); http://dx.doi.org/10.1063/1.2192579 (3 pages) | Cited 6 times

Online Publication Date: 31 March 2006

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We show that SnO2 nanoclusters in silica interact with ultrashort infrared laser pulses focused inside the material generating a hydrostatic compression and photoelastic response of the surrounding glass. This effect, together with the laser-induced nanocluster amorphization, gives rise to positive or negative refractive-index changes, up to 10−2, depending on the beam-power density. This result points out a wide tuning of the refractive index patterns obtainable in silica-based optical technology.
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78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
42.86.+b Optical workshop techniques
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Rx Nanocrystalline materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.16.-c Methods of micro- and nanofabrication and processing

Effects of Ag/indium tin oxide contact to a SiC doping layer on performance of Si nanocrystal light-emitting diodes

Chul Huh, Nae-Man Park, Jae-Heon Shin, Kyung-Hyun Kim, Tae-Youb Kim, Kwan Sik Cho, and Gun Yong Sung

Appl. Phys. Lett. 88, 131913 (2006); http://dx.doi.org/10.1063/1.2191409 (3 pages) | Cited 10 times

Online Publication Date: 31 March 2006

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We report on the effects of a very thin Ag (2.5 nm) interlayer between the indium tin oxide (ITO) current spreading layer and a SiC doping layer on silicon nanocrystals (nc-Si) embedded in silicon nitride film on the electrical and optical performance of the light-emitting diodes (LEDs). The forward voltage at a current of 20 mA of the nc-Si LED with a Ag interlayer was decreased by 2.5 V compared to that of the nc-Si LED without one due to the decrease in the contact resistance. In addition, the light output power of the nc-Si LED with a Ag interlayer was also enhanced by 40%. This result strongly indicates that the Ag/ITO contact scheme can serve as a highly promising contact scheme to a SiC film for the realization of the nc-Si LEDs with a high efficiency.
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85.60.Jb Light-emitting devices

Atomic structure of (111) SrTiO3/Pt interfaces

Steffen Schmidt, Dmitri O. Klenov, Sean P. Keane, Jiwei Lu, Thomas E. Mates, and Susanne Stemmer

Appl. Phys. Lett. 88, 131914 (2006); http://dx.doi.org/10.1063/1.2191410 (3 pages) | Cited 4 times

Online Publication Date: 31 March 2006

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Atomic resolution high-angle annular dark field (HAADF) imaging in scanning transmission electron microscopy was used to investigate the interface atomic structure of epitaxial, (111) oriented SrTiO3 films on epitaxial Pt electrodes grown on (0001) sapphire. The cube-on-cube orientation relationship of SrTiO3 on Pt was promoted by the use of a Ti adhesion layer underneath the Pt electrode. While a Ti-rich Pt surface was observed before SrTiO3 growth, HAADF images showed an atomically abrupt SrTiO3/Pt interface with no interfacial layers. The SrTiO3 films contained two twin variants that were related by a 180° rotation about the ⟨111⟩ surface normal. HAADF images showed two different interface atomic arrangements for the two twins. The role of Ti in promoting (111) epitaxy and the implications for the dielectric properties are discussed.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
68.37.Lp Transmission electron microscopy (TEM)
68.55.-a Thin film structure and morphology
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Discovery of the deep level related to hydrogen in anatase TiO2

Takahira Miyagi, Masayuki Kamei, Takefumi Mitsuhashi, and Atsushi Yamazaki

Appl. Phys. Lett. 88, 132101 (2006); http://dx.doi.org/10.1063/1.2191090 (3 pages)

Online Publication Date: 27 March 2006

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Deep level transient spectroscopy was carried out to investigate the origin of the deep levels in the band gap of anatase TiO2. The epitaxial anatase-TiO2 film grown by metal-organic chemical vapor deposition possessed a deep level whose activation energy was 0.52 eV. In contrast, this deep level at 0.5 eV was not observed in the films grown by sputtering. However, by adding CH4 or H2 to the sputtering gas, the deep level at 0.5 eV was observed in the sputter-grown films. Furthermore, the density of this deep level increased with increasing hydrogen gas, suggesting that this deep level originated from hydrogen doping.
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71.55.Ht Other nonmetals
71.20.Nr Semiconductor compounds
61.72.up Other materials

Room-temperature electroluminescence of AlSb/InAsSb single quantum wells grown by metal organic vapor phase epitaxy

K. D. Moiseev, E. V. Ivanov, G. G. Zegrya, M. P. Mikhailova, Yu. P. Yakovlev, E. Hulicius, A. Hospodková, J. Pangrác, K. Melichar, and T. Šimeček

Appl. Phys. Lett. 88, 132102 (2006); http://dx.doi.org/10.1063/1.2189572 (3 pages) | Cited 2 times

Online Publication Date: 27 March 2006

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Intense mid-infrared (λ ∼ 2 μm) room temperature electroluminescence from metal organic vapor phase epitaxy (MOVPE) grown type-I single AlSb/InAsSb/AlSb quantum wells (QWs) is reported. The spectral position of the electroluminescent peaks is in good agreement with k∙p envelope function calculation in the frame of four-band Kane’s model taking into account the intermixing of s and p states in the deep quantum well. A four times increase of the emission intensity with temperature increasing from 77 to 300 K can be explained by highly efficient radiative recombination of the electrons injected into the narrow AlSb/InAsSb/AlSb QW due to its specific design, leading to Auger process suppression.
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73.21.Fg Quantum wells
78.60.Fi Electroluminescence
78.67.De Quantum wells
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Si and SiO2 layer transfer induced by mechanical residual stress

V. Loryuenyong and N. W. Cheung

Appl. Phys. Lett. 88, 132103 (2006); http://dx.doi.org/10.1063/1.2189669 (3 pages) | Cited 1 time

Online Publication Date: 27 March 2006

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Using the polymer SU-8 as a bonding and stress-inducing layer, we have demonstrated that Si and SiO2 layers can be transferred by mechanical cleavage to SU-8/glass substrates without ion implantation of the donor wafers. Cracks tend to propagate under mode II criterion (KII = 0) at a characteristic depth defined by the residual stress and elastic properties of the Si/SU-8/glass matrix. An analytical model is developed and verified for the dependence of the measured characteristic crack depth on the elastic modulus of substrate materials.
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68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Current transport studies of ZnO/p-Si heterostructures grown by plasma immersion ion implantation and deposition

X. D. Chen, C. C. Ling, S. Fung, C. D. Beling, Y. F. Mei, Ricky K. Y. Fu, G. G. Siu, and Paul. K. Chu

Appl. Phys. Lett. 88, 132104 (2006); http://dx.doi.org/10.1063/1.2190444 (3 pages) | Cited 25 times

Online Publication Date: 27 March 2006

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Rectifying undoped and nitrogen-doped ZnO/p-Si heterojunctions were fabricated by plasma immersion ion implantation and deposition. The undoped and nitrogen-doped ZnO films were n type (n ∼ 1019 cm−3) and highly resistive (resistivity ∼ 105 Ω cm), respectively. While forward biasing the undoped-ZnO/p-Si, the current follows Ohmic behavior if the applied bias Vforward is larger than ∼ 0.4 V. However, for the nitrogen-doped-ZnO/p-Si sample, the current is Ohmic for Vforward<1.0 V and then transits to J ∼ V2 for Vforward>2.5 V. The transport properties of the undoped-ZnO/p-Si and the N-doped-ZnO/p-Si diodes were explained in terms of the Anderson model and the space charge limited current model, respectively.
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81.05.Dz II-VI semiconductors
81.05.Cy Elemental semiconductors
81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.77.Dq Plasma-based ion implantation and deposition
61.72.uf Ge and Si
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Behavior of antimony in ZnSe grown by a closed Bridgman method

J. F. Wang and M. Isshiki

Appl. Phys. Lett. 88, 132105 (2006); http://dx.doi.org/10.1063/1.2190271 (3 pages)

Online Publication Date: 28 March 2006

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High-quality and large-size p-ZnSe single crystals doped with antimony (Sb) have been grown by a Bridgman method using a closed double crucible. Photoluminescence spectra at low temperatures indicate that Sb works as both a shallow acceptor and a deep complex donor. By studying the temperature and excitation intensity dependences of the free-to-acceptor and donor-acceptor pair emissions, we estimated that the ionization energy of Sb as a shallow acceptor in ZnSe is (112–114) meV above the valence band, and that of the deep complex donor related to Sb is 37 ±1 meV below the conduction band.
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71.55.Gs II-VI semiconductors
78.55.Et II-VI semiconductors
81.10.Fq Growth from melts; zone melting and refining
61.72.uj III-V and II-VI semiconductors
81.05.Dz II-VI semiconductors

Controlling field-effect mobility in pentacene-based transistors by supersonic molecular-beam deposition

T. Toccoli, A. Pallaoro, N. Coppedè, S. Iannotta, F. De Angelis, L. Mariucci, and G. Fortunato

Appl. Phys. Lett. 88, 132106 (2006); http://dx.doi.org/10.1063/1.2187494 (3 pages) | Cited 16 times

Online Publication Date: 28 March 2006

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We show that pentacene field-effect transistors, fabricated by supersonic molecular beams, have a performance strongly depending on the precursor’s kinetic energy (KE). The major role played by KE is in achieving highly ordered and flat films. In the range KE ≈ 3.5–6.5 eV, the organic field effect transistor linear mobility increases of a factor ∼ 5. The highest value (1.0 cm2 V−1 s−1) corresponds to very uniform and flat films (layer-by-layer type growth). The temperature dependence of mobility for films grown at KE>6 eV recalls that of single crystals (bandlike) and shows an opposite trend for films grown at KE ⩽ 5.5 eV.
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85.30.Tv Field effect devices
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Subnanometer-equivalent-oxide-thickness germanium p-metal-oxide-semiconductor field effect transistors fabricated using molecular-beam-deposited high-k/metal gate stack

A. Ritenour, A. Khakifirooz, D. A. Antoniadis, R. Z. Lei, W. Tsai, A. Dimoulas, G. Mavrou, and Y. Panayiotatos

Appl. Phys. Lett. 88, 132107 (2006); http://dx.doi.org/10.1063/1.2189456 (3 pages) | Cited 36 times

Online Publication Date: 28 March 2006

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Metal-oxide-semiconductor field effect transistors (MOSFET) with a thin high-k dielectric were fabricated on bulk n-type germanium substrates. Surface oxides were thermally desorbed in situ by heating the substrates under ultrahigh vacuum conditions. First an ultrathin passivating layer was formed by evaporating germanium in the presence of atomic oxygen and nitrogen supplied from a remote radio frequency plasma source. Subsequently, the HfO2 dielectric was deposited by evaporating hafnium in the presence of atomic oxygen. An in situ TaN metal gate was similarly deposited. Long channel devices were fabricated using a standard process flow. These devices exhibited a low equivalent oxide thickness (EOT) of 0.7 nm with gate leakage less than 15 mA/cm2 at VFB+1 V. Device mobility was extracted from Is-Vg and split C-V characteristics. Results indicate a 2× mobility enhancement in Ge p-MOSFET devices compared to Si control devices. The demonstration of subnanometer EOT suggests that high-k gate dielectrics on germanium are scalable to low EOT and suitable for use in ultrascaled MOSFET devices.
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85.30.Tv Field effect devices

Molecular beam epitaxy growth of In0.52Al0.48As/In0.53Ga0.47As metamorphic high electron mobility transistor employing growth interruption and in situ rapid thermal annealing

Soo-Ghang Ihn, Seong June Jo, and Jong-In Song

Appl. Phys. Lett. 88, 132108 (2006); http://dx.doi.org/10.1063/1.2189607 (3 pages) | Cited 1 time

Online Publication Date: 28 March 2006

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We investigated the effects of high temperature ( ∼ 700 °C) in situ rapid thermal annealing (RTA) carried out during growth interruption between spacer and δ-doping layers of an In0.52Al0.48As/In0.53Ga0.47As metamorphic high electron mobility transistor (MHEMT) grown on a compositionally graded InGaAlAs buffer layer. The in situ RTA improved optical and structural properties of the MHEMT without degradation of transport property, while postgrowth RTA improved the structural property of the MHEMT but significantly degraded mobility due to the defect-assisted Si diffusion. The results indicate the potential of the in situ RTA for use in the growth of high-quality metamorphic epitaxial layers for optoelectronic applications requiring improved optical and electrical properties.
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85.30.Tv Field effect devices
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Thermally stimulated current studies on neutron irradiation induced defects in GaN

K. Kuriyama, M. Ooi, A. Onoue, K. Kushida, M. Okada, and Q. Xu

Appl. Phys. Lett. 88, 132109 (2006); http://dx.doi.org/10.1063/1.2190446 (3 pages) | Cited 5 times

Online Publication Date: 28 March 2006

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The evaluation of the neutron irradiation induced defects in GaN is studied using a thermally stimulated current (TSC) method with excitation above (below) the energy band gap using ultraviolet (blue, green, red, and infrared) emitting diodes. Annealing at 1000 °C, a broad TSC spectrum for excitation by the ultraviolet light is resolved by five traps, P1 (ionization energy is 200 meV), P2 (270 meV), P3 (380 meV), P4 (490 meV), and P5 (595 meV). Infrared illumination shows a remarkable reduction in TSC for the P2 and P3 traps, indicating the photoquenching behavior. The possible origins of the observed five traps are discussed.
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73.61.Ey III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.55.Eq III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors

HgCdTe superlattices for solid-state cryogenic refrigeration

Daryoosh Vashaee and Ali Shakouri

Appl. Phys. Lett. 88, 132110 (2006); http://dx.doi.org/10.1063/1.2191094 (3 pages) | Cited 2 times

Online Publication Date: 29 March 2006

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A tall barrier superlattice structure based on mercury cadmium telluride material system is proposed that can achieve a large effective thermoelectric figure of merit (ZTmax ∼ 3) at cryogenic temperatures. Calculations based on the Boltzmann transport equation taking into account the quantum mechanical electron transmission show that the Seebeck coefficient can be increased significantly at low temperatures with the use of nonplanar barriers as the thermal spreading of the electron density is tightened around the Fermi level. This provides a better asymmetric differential conductivity around the Fermi level close to the top of the barrier. Consequently, a high thermoelectric power factor is produced resulting in a large ZT.
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72.20.Pa Thermoelectric and thermomagnetic effects
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Electron energy band alignment at interfaces of (100)Ge with rare-earth oxide insulators

V. V. Afanas’ev, S. Shamuilia, A. Stesmans, A. Dimoulas, Y. Panayiotatos, A. Sotiropoulos, M. Houssa, and D. P. Brunco

Appl. Phys. Lett. 88, 132111 (2006); http://dx.doi.org/10.1063/1.2191736 (3 pages) | Cited 22 times

Online Publication Date: 31 March 2006

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Energy diagrams of interfaces between (100)Ge and several rare-earth oxide insulators deposited from a molecular beam are determined using a combination of internal photoemission and photoconductivity measurements. For the wide band gap (5.9 eV) oxides Gd2O3 and LaHfOx, the band alignment at the interface is found to be close to that of HfO2 and is characterized by conduction/valence band offsets of ∼ 2/ ∼ 3 eV. In contrast, CeO2 which has a much narrower band gap (3.3 eV) does not provide a band alignment diagram corresponding to sufficient insulation.
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73.20.-r Electron states at surfaces and interfaces
79.60.Jv Interfaces; heterostructures; nanostructures
72.40.+w Photoconduction and photovoltaic effects

Analytical model for incomplete signal generation in semiconductor detectors

Ho Kyung Kim

Appl. Phys. Lett. 88, 132112 (2006); http://dx.doi.org/10.1063/1.2191742 (3 pages) | Cited 3 times

Online Publication Date: 31 March 2006

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Signal generation from semiconductor detectors has been modeled considering incomplete charge signal due to the charge trapping within a detector as well as to the ballistic deficit caused by insufficient charge collection time. The analytical formalism was experimentally confirmed with the charge collection efficiency of a planar mercuric iodide (HgI2) detector. The developed model is useful for the characterization of detector material properties such as the mobility and the lifetime, as well as the optimization of operation conditions such as the applied bias and the charge collection time.
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85.60.-q Optoelectronic devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Ultrafast spectroscopy of impact ionization and avalanche multiplication in GaAs

S. Trumm, M. Betz, F. Sotier, A. Leitenstorfer, A. Schwanhäußer, M. Eckardt, O. Schmidt, S. Malzer, G. H. Döhler, M. Hanson, D. Driscoll, and A. C. Gossard

Appl. Phys. Lett. 88, 132113 (2006); http://dx.doi.org/10.1063/1.2191880 (3 pages) | Cited 3 times

Online Publication Date: 31 March 2006

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Femtosecond carrier dynamics in biased AlxGa1−xAs heterostructure diodes is investigated tracing transient modifications of the Franz-Keldysh absorption spectrum. The nonlinear optical response is sensitive to the number of electron-hole pairs in the high-field region of the sample. As a result, the dynamical buildup of a nonequilibrium carrier avalanche due to impact ionization for electric fields F ≥ 350 kV/cm is directly analyzed in the time domain. The time scale of the carrier multiplication is found to be in the order of 10 ps depending on the number of photoinjected carriers. Monte Carlo simulations in a simplified band structure agree well with the experiment.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Ht High-field and nonlinear effects
78.47.-p Spectroscopy of solid state dynamics
85.30.Kk Junction diodes

Control of p- and n-type conductivities in P doped ZnO thin films by using radio-frequency sputtering

Zhi Gen Yu, Ping Wu, and Hao Gong

Appl. Phys. Lett. 88, 132114 (2006); http://dx.doi.org/10.1063/1.2192089 (3 pages) | Cited 23 times

Online Publication Date: 31 March 2006

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The conduction type of P doped ZnO thin films using Zn3P2 dopant source can be controlled by adjusting the oxygen partial pressure by means of radio-frequency sputtering. Under an optimal oxygen partial pressure of 5%, p-type ZnO thin films were obtained with a hole concentration of 1.93×1016–3.84×1019 cm−3. Under a growth condition of extremely low oxygen partial pressure, P doped ZnO thin films exhibit n-type conduction with a hole concentration of 8.34×1017–3.1×1019 cm−3. This research not only achieved significant technical advance in the fabrication of p-type ZnO but also gained critical advance in fundamental understanding of the governing mechanism of p-type ZnO.
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81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth
73.61.Ga II-VI semiconductors
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Superconducting π qubit with three Josephson junctions

T. Yamashita, S. Takahashi, and S. Maekawa

Appl. Phys. Lett. 88, 132501 (2006); http://dx.doi.org/10.1063/1.2189191 (3 pages) | Cited 14 times

Online Publication Date: 27 March 2006

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We propose a qubit consisting of a superconducting ring with two zero junctions and one ferromagnetic π junction. In the system, degenerate states appear in the phase space without an external magnetic field because of a competition between the zero and π states. Quantum tunneling between the degenerate states leads to a formation of bonding and antibonding states which are used as a bit. For manipulating the states, only a small magnetic field around zero is required. This feature leads to a large-scale integration and a construction of the smaller-sized qubit which is robust to the decoherence by external noises.
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03.67.Lx Quantum computation architectures and implementations
74.50.+r Tunneling phenomena; Josephson effects
74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
85.25.Cp Josephson devices

Investigations on electroresistance effect in epitaxial manganite films using field effect configurations

F. X. Hu and J. Gao

Appl. Phys. Lett. 88, 132502 (2006); http://dx.doi.org/10.1063/1.2189197 (3 pages) | Cited 15 times

Online Publication Date: 27 March 2006

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The influence of static electric field on the transport properties in La0.7A0.3MnO3 (A = Ca,Ba) epitaxial thin films was investigated by using field effect configurations (FEC). A single layer manganite film was deposited on LaAlO3 (LAO) substrate by pulsed laser deposition technique, and then a simple FEC was formed on it using the lithography technique, in which the manganite film was used as a channel, and the LAO substrate as a gate. Surprising results were achieved by employing such a FEC. The transport resistance increases with a positive gate voltage but decreases with a negative bias, which means the electroresistance (ER) effect changes sign with the field direction. The observed reduction of resistivity for the La0.7Ca0.3MnO3 and La0.7Ba0.3MnO3 channels reaches ∼ 32% and ∼ 34% upon a bias of −80  and −300 V, respectively. The films could completely return to their pristine state after the bias was removed and the ER effect could be fully reproduced.
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73.61.-r Electrical properties of specific thin films
81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth
75.70.-i Magnetic properties of thin films, surfaces, and interfaces

Magnetocaloric effect in Ni–Fe–Ga shape memory alloys

V. Recarte, J. I. Pérez-Landazábal, C. Gómez-Polo, E. Cesari, and J. Dutkiewicz

Appl. Phys. Lett. 88, 132503 (2006); http://dx.doi.org/10.1063/1.2189665 (3 pages) | Cited 22 times

Online Publication Date: 27 March 2006

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The magnetic entropy change in three different polycrystalline Ni53+xFe20−xGa27 (x = 0.5,1,2) alloys was analyzed as a function of temperature under different applied magnetic fields. The temperature dependence of the ac magnetic susceptibility (χ) and the magnetization of the alloys have been used to characterize the different structural and magnetic transformations. In spite of the different magnetic states, the alloys show comparable magnetic entropy values. For x ⩽ 1 the martensitic transformation takes place in the ferromagnetic state for measuring temperatures below room temperature, whereas the alloy with x = 2 displays the martensitic transformation above room temperature between two paramagnetic phases. Maximum values of the magnetic entropy change are correlated with the martensitic transformation, irrespective of the particular magnetic state (ferromagnetic or paramagnetic) during the transformation.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Bb Fe and its alloys
64.70.K- Solid-solid transitions
81.30.Kf Martensitic transformations
81.40.Lm Deformation, plasticity, and creep
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Large magnetic anisotropy in the quasi-one-dimensional system BaCo2V2O8

Zhangzhen He, Tomoyasu Taniyama, and Mitsuru Itoh

Appl. Phys. Lett. 88, 132504 (2006); http://dx.doi.org/10.1063/1.2189913 (3 pages) | Cited 10 times

Online Publication Date: 27 March 2006

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Magnetic anisotropy in the one-dimensional spin chain system BaCo2V2O8 is investigated using magnetic susceptibility, magnetization, and heat capacity measurements. Unusual magnetic anisotropy is observed in the paramagnetic state at room temperature. The magnetic anisotropy energy of BaCo2V2O8 is estimated to be greater than 1.44(4)×107 erg/cm3 at 2 K using a simple uniaxial two-sublattice mean-field model.
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75.50.Ee Antiferromagnetics
75.30.Gw Magnetic anisotropy
75.30.Cr Saturation moments and magnetic susceptibilities
75.20.Ck Nonmetals
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)

Observation of field-induced reverse transformation in ferromagnetic shape memory alloy Ni50Mn36Sn14

Keiichi Koyama, Kazuo Watanabe, Takeshi Kanomata, Ryosuke Kainuma, Katsunari Oikawa, and Kiyohito Ishida

Appl. Phys. Lett. 88, 132505 (2006); http://dx.doi.org/10.1063/1.2189916 (3 pages) | Cited 73 times

Online Publication Date: 27 March 2006

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The structural and magnetic properties of the ferromagnetic Heusler alloy Ni50Mn36Sn14 were studied by magnetization and x-ray powder diffraction measurements in fields up to 5 T. The alloy undergoes the martensitic transformation from the L21-type cubic structure with the lattice parameter ac = 0.5988 nm into an orthorhombic structure with the lattice parameters ao = 0.8617 nm, bo = 0.5702 nm and co = 0.4359 nm at Ms = 220 K with a thermal hysteresis of 40 K. The cell volume contracts by 0.37% and the magnetic moment decreases by 50% at Ms. Furthermore, we directly observed the field-induced reverse martensitic transformation.
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64.70.K- Solid-solid transitions
81.30.Kf Martensitic transformations
75.50.Cc Other ferromagnetic metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.66.Dk Alloys
75.30.Cr Saturation moments and magnetic susceptibilities

Micromagnetic investigation of the dynamics of magnetization switching induced by a spin polarized current

Kyung-Jin Lee and Bernard Dieny

Appl. Phys. Lett. 88, 132506 (2006); http://dx.doi.org/10.1063/1.2190450 (3 pages) | Cited 18 times

Online Publication Date: 27 March 2006

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Using micromagnetic modeling, we tested a prediction of single-domain spin-torque theory which switching current density depends only weakly on magnetic cell size. The switching time and current density are strongly affected by the cell size for low spin polarization. Larger samples with a small length-to-width ratio and small spin polarization can exhibit a nonmonotonous dependence of switching time on current. Excitation of incoherent spin waves caused by the circular Oersted field due to the current is responsible for this nonmonotonous dependence. However, the magnetic dynamics recovers a single-domain-like behavior when the spin polarization is high and/or the cell size is small.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.25.-b Spin polarized transport
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