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14 Sep 2009

Volume 95, Issue 11, Articles (11xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 95, 113101 (2009); http://dx.doi.org/10.1063/1.3197646 (3 pages)

Jesse J. Cole, En-Chiang Lin, Chad R. Barry, and Heiko O. Jacobs
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Electron diffractive imaging of nano-objects using a guided method with a dynamic support

Roman Dronyak, Keng S. Liang, Yuri P. Stetsko, Ting-Kuo Lee, Chi-Kai Feng, Jin-Sheng Tsai, and Fu-Rong Chen

Appl. Phys. Lett. 95, 111908 (2009); http://dx.doi.org/10.1063/1.3227837 (3 pages) | Cited 8 times

Online Publication Date: 15 September 2009

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We present a phase recovery technique that utilizes a guiding method with a dynamic support to reconstruct the shape and exit wave of a single MgO nanoparticle in a coherent electron diffraction experiment. The proposed method provides an optimal solution deduced from the electron diffraction pattern alone. The recovered shape has spatial resolution 3.1 nm. The complex exit wave encodes the projected atomic structure of the nanocrystal with resolution about 0.15 nm, and agrees with a multislice simulation. The possibility of imaging nanosized objects at diffraction-limited resolution using a field emission electron microscope is thus demonstrated.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
68.37.Vj Field emission and field-ion microscopy

Influence of surface morphology on the optical property of vertically aligned ZnO nanorods

Sachindra Nath Das, Jyoti Prakash Kar, Ji-Hyuk Choi, S. Byeon, Y. D. Jho, and Jae-Min Myoung

Appl. Phys. Lett. 95, 111909 (2009); http://dx.doi.org/10.1063/1.3231615 (3 pages) | Cited 5 times

Online Publication Date: 17 September 2009

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In this letter we have studied an influence of surface morphology on the optical property of vertically aligned ZnO nanorods. At low temperature the near band edge excitonic emission shows a strong dependence on surface morphology. A prominent and well resolved near band edge photoluminescence (PL) peak was obtained for nanowires with decreasing diameter and thus assigned due to the contributions to the optical properties of individual nanorods. Depending on surface morphology, the difference in low temperature PL property is attributed to the tailing of the density of states due to the potential fluctuations in randomly distributed intrinsic defects.
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78.67.Lt Quantum wires
73.22.Lp Collective excitations
78.68.+m Optical properties of surfaces
73.21.Hb Quantum wires
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
68.35.bg Semiconductors

Diffusion of hydrogen vacancy in Na3AlH6

Jianchuan Wang, Yong Du, Honghui Xu, Lixian Sun, and Zi-kui Liu

Appl. Phys. Lett. 95, 111910 (2009); http://dx.doi.org/10.1063/1.3225152 (3 pages) | Cited 2 times

Online Publication Date: 17 September 2009

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We perform first-principles calculations to investigate neutral and charged H vacancies dynamics involving vacancy formation and diffusion in Na3AlH6. We find that the activation barrier for local diffusion (diffusion within AlH5 unit) is smaller than that of nonlocal diffusion (diffusion between AlH6 and AlH5 units) for all types of H vacancies; H diffusion in Na3AlH6 is dominated by mobility of positively charged H vacancies. Furthermore, our results confirm that the observed highly mobile species by anelastic spectroscopy measurements is probably the positively charged H vacancies in the form of local diffusion.
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66.30.Lw Diffusion of other defects
84.60.-h Direct energy conversion and storage
61.72.jd Vacancies

Single-shot ultrafast electron diffraction with a laser-accelerated sub-MeV electron pulse

Shigeki Tokita, Shunsuke Inoue, Shinichiro Masuno, Masaki Hashida, and Shuji Sakabe

Appl. Phys. Lett. 95, 111911 (2009); http://dx.doi.org/10.1063/1.3226674 (3 pages) | Cited 4 times

Online Publication Date: 17 September 2009

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We have demonstrated single-shot measurement of electron diffraction patterns for a single-crystal gold foil using 340 keV electron pulses accelerated by intense femtosecond laser pulses with an intensity of 2×1018 W/cm2. The measured electron beam profile is faithfully reproduced by the numerical simulation of the electron trajectory, providing evidence that the electron pulse spontaneously expands in time owing to the velocity spread produced in the acceleration process, but is not distorted in an irreversible nonlinear manner. This study shows that the laser acceleration is promising for the development of pulse compression methods for single-shot femtosecond electron diffraction.
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61.05.J- Electron diffraction and scattering
06.60.Jn High-speed techniques (microsecond to femtosecond)

Blister formation in ion-implanted GaAs: Role of diffusivity

R. R. Collino, B. B. Dick, F. Naab, Y. Q. Wang, M. D. Thouless, and R. S. Goldman

Appl. Phys. Lett. 95, 111912 (2009); http://dx.doi.org/10.1063/1.3224199 (3 pages) | Cited 4 times

Online Publication Date: 17 September 2009

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We have investigated the influence of substrate temperature during implantation, Timplant, on blister formation in GaAs:N layers produced by N ion implantation followed by rapid thermal annealing. Similar depths of popped blisters (craters) and damage profiles were observed for both low and high Timplant. This is in contrast to reports of Timplant-dependent blister formation in higher-diffusivity systems such as GaAs:H and Si:H. The apparent Timplant-insensitivity of blister formation in GaAs:N is likely due to the lower diffusivity of N in GaAs in comparison to that of H in GaAs and Si.
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81.05.Ea III-V semiconductors
66.30.H- Self-diffusion and ionic conduction in nonmetals
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
61.72.uj III-V and II-VI semiconductors
68.55.ag Semiconductors

Broadband optical amplification in silicate glass ceramics containing Li2ZnSiO4:Cr4+ nanocrystals

Yixi Zhuang, Yu Teng, Jin Luo, Bin Zhu, Yingzhi Chi, E Wu, Heping Zeng, and Jianrong Qiu

Appl. Phys. Lett. 95, 111913 (2009); http://dx.doi.org/10.1063/1.3231439 (3 pages) | Cited 6 times

Online Publication Date: 18 September 2009

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Transparent glass ceramics containing Li2ZnSiO4:Cr4+ nanocrystals are prepared and their optical properties are investigated. The glass ceramics show intense broadband infrared luminescence and long fluorescence lifetime of about 90 μs. The single-pass optical amplification is demonstrated on a traditional two-wave mixing configuration. The optical gain efficiency is about 1.27 cm−1 when the excitation power is 0.80 W. The optical gain shows the similar wavelength dependence with luminescence properties. The transparent glass ceramics containing Li2ZnSiO4:Cr4+ nanocrystals have potential application as broadband gain media in optical communication system.
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81.05.Pj Glass-based composites, vitroceramics
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.47.nj Four-wave mixing spectroscopy
81.07.Bc Nanocrystalline materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.70.Ce Glasses, quartz
78.55.Hx Other solid inorganic materials

Twin Cu nanowires using energetic beams

Yongfeng Zhang and Hanchen Huang

Appl. Phys. Lett. 95, 111914 (2009); http://dx.doi.org/10.1063/1.3232240 (3 pages) | Cited 3 times

Online Publication Date: 18 September 2009

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It is well established that twinning can increase the mechanical strength of metallic (such as Cu) nanowires. This letter proposes a method of introducing twin boundaries into Cu nanowires using energetic beams and demonstrates the feasibility through classical molecular dynamics simulations. The authors show that after electron bombardment twinning occurs in Cu nanowires. The twinning consists of three steps: nucleation of hexagonal-close-packed (HCP) layer, growth of the HCP layer, and interaction of nearby HCP layers. The twinning method reported here offers a mechanism of improving the mechanical strength of metallic nanowires.
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81.07.Vb Quantum wires
62.23.Hj Nanowires
61.72.Mm Grain and twin boundaries
61.43.Bn Structural modeling: serial-addition models, computer simulation
61.80.Fe Electron and positron radiation effects

Semiconductor to metal transition characteristics of VO2 thin films grown epitaxially on Si (001)

A. Gupta, R. Aggarwal, P. Gupta, T. Dutta, Roger J. Narayan, and J. Narayan

Appl. Phys. Lett. 95, 111915 (2009); http://dx.doi.org/10.1063/1.3232241 (3 pages) | Cited 16 times

Online Publication Date: 18 September 2009

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We report semiconductor to metal transition (SMT) characteristics of vanadium dioxide (VO2) grown epitaxially on Si (001) at 500 °C. The epitaxial integration with Si (001) was achieved by using epitaxial tetragonal yttria-stabilized zirconia (YSZ) as an intermediate buffer layer, which was grown in situ. From x-ray (θ-2θ and ϕ-scan) and electron diffraction studies, we established that VO2 and YSZ grow in (020) and (001) orientations, respectively, on Si (001) substrate and epitaxial relationship was established to be “VO2[001] or VO2[100]”//YSZ[110]//Si [100] and VO2(010)//YSZ(001)//Si(001). VO2/YSZ/Si(001) heterostructures showed approximately three orders of magnitude reversible change in resistivity and hysteresis of ∼ 6 K upon traversing the transition temperature. A 10 °C increase in the SMT temperature of these VO2 films, compared to the value reported for bulk VO2, has been explained on the basis of uniaxial stress along the c-axis, which can stabilize the covalent monoclinic phase up to higher temperatures. A correlation between in-plane orientations of the film and the transition width has also been suggested, which is consistent with our previously published thermodynamic model.
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71.30.+h Metal-insulator transitions and other electronic transitions
72.60.+g Mixed conductivity and conductivity transitions
68.60.Bs Mechanical and acoustical properties
68.55.A- Nucleation and growth
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Ng Insulators
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E centers in ternary Si1−x−yGexSny random alloys

A. Chroneos, C. Jiang, R. W. Grimes, U. Schwingenschlögl, and H. Bracht

Appl. Phys. Lett. 95, 112101 (2009); http://dx.doi.org/10.1063/1.3224894 (3 pages) | Cited 21 times

Online Publication Date: 14 September 2009

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Density functional theory calculations are used to study the association of arsenic (As) atoms to lattice vacancies and the formation of As-vacancy pairs, known as E centers, in the random Si0.375Ge0.5Sn0.125 alloy. The local environments are described by 32-atom special quasirandom structures that represent random Si1−x−yGexSny alloys. It is predicted that the nearest-neighbor environment will exert a strong influence on the stability of E centers in ternary Si0.375Ge0.5Sn0.125.
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61.72.jn Color centers
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
61.72.jd Vacancies

Bandgap and band offsets determination of semiconductor heterostructures using three-terminal ballistic carrier spectroscopy

Wei Yi, Venkatesh Narayanamurti, Hong Lu, Michael A. Scarpulla, Arthur C. Gossard, Yong Huang, Jae-Hyun Ryou, and Russell D. Dupuis

Appl. Phys. Lett. 95, 112102 (2009); http://dx.doi.org/10.1063/1.3224914 (3 pages) | Cited 2 times

Online Publication Date: 14 September 2009

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Utilizing ambipolar tunnel emission of ballistic electrons and holes, we have developed a model-independent method to self-consistently measure bandgaps of semiconductors and band offsets at semiconductor heterojunctions. Lattice-matched GaAs/AlxGa1−xAs and GaAs/(AlxGa1−x)0.51In0.49P (100) single-barrier heterostructures are studied at 4.2 K. For the GaAs/AlGaAs interface, the measured Γ band offset ratio is 60.4:39.6 (±2%). For the heteroanion GaAs/AlGaInP (100) interface, this ratio varies with the Al composition and is distributed more in the valence band. The indirect-gap X band offsets observed at the GaAs/AlGaInP interface deviates from predictions by the transitivity rule.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.80.Ey III-V and II-VI semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.60.Jv Interfaces; heterostructures; nanostructures
71.20.Nr Semiconductor compounds
72.20.Ht High-field and nonlinear effects
73.23.Ad Ballistic transport

Photoluminescence-based measurements of the energy gap and diffusion length of Zn3P2

Gregory M. Kimball, Astrid M. Müller, Nathan S. Lewis, and Harry A. Atwater

Appl. Phys. Lett. 95, 112103 (2009); http://dx.doi.org/10.1063/1.3225151 (3 pages) | Cited 7 times

Online Publication Date: 14 September 2009

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The steady-state photoluminescence spectra of zinc phosphide (Zn3P2) wafers have revealed a fundamental indirect band gap at 1.38 eV, in close proximity to the direct band gap at 1.50 eV. These values are consistent with the values for the indirect and direct band gaps obtained from analysis of the complex dielectric function deduced from spectroscopic ellipsometric measurements. Bulk minority carrier lifetimes of 20 ns were observed by time-resolved photoluminescence decay measurements, implying minority-carrier diffusion lengths of ≥ 7 μm.
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78.55.Hx Other solid inorganic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.47.jd Time resolved luminescence
72.80.Jc Other crystalline inorganic semiconductors

Electrical behavior of electrospun heterostructured Ag–ZnO nanofibers

Dandan Lin, Hui Wu, Xiaolu Qin, and Wei Pan

Appl. Phys. Lett. 95, 112104 (2009); http://dx.doi.org/10.1063/1.3227691 (3 pages) | Cited 2 times

Online Publication Date: 15 September 2009

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In this work, the electrical behavior of heterostructured Ag–ZnO nanofibers was studied by varying the Ag content. The electric conductivity of the hybrids follows the percolation theory and can reach as high as 115 S cm−1 due to the electron transfer highway provided by Ag phase. Typical low-voltage varistor behavior, with nonlinear coefficient of ∼ 10, was observed for samples with proper Ag concentration. Possible mechanism was elucidated by means of the morphology and distribution of Ag additives throughout the ZnO host.
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81.07.Bc Nanocrystalline materials
73.63.Bd Nanocrystalline materials
85.30.-z Semiconductor devices

Assessment of thermoelectric performance of Cu2ZnSnX4, X = S, Se, and Te

C. Sevik and T. Çağın

Appl. Phys. Lett. 95, 112105 (2009); http://dx.doi.org/10.1063/1.3222862 (3 pages) | Cited 19 times

Online Publication Date: 16 September 2009

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A recent experiment on In-doped Cu2ZnSnSe4 [ X. Y. Shi et al., Appl. Phys. Lett. 94, 122103 (2009) ] has shown promising thermoelectric performance characteristics. In this letter, we analyze relevant electronic and transport properties of Cu2ZnSnSe4 and similar compounds, Cu2ZnSnS4 and Cu2ZnSnTe4, to assess their potential as thermoelectric materials. Using density functional theory and Boltzmann transport equations, we determine Seebeck coefficients, conductivities, and power factors of closely related polymorphs with space groups, Imath, Imath2m, and Pmath2m for each compound. Based on their electronic structure and transport properties, we conclude that other two compounds could have similar potential as thermoelectric materials.
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72.15.Jf Thermoelectric and thermomagnetic effects
71.20.Be Transition metals and alloys
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling

Transmission electron microscopy investigation of inversion domain boundary in Al0.65Ga0.35N grown on AlN/sapphire template

L. W. Sang, H. Fang, Z. X. Qin, X. Q. Wang, B. Shen, Z. J. Yang, G. Y. Zhang, X. P. Zhang, L. P. You, and D. P. Yu

Appl. Phys. Lett. 95, 112106 (2009); http://dx.doi.org/10.1063/1.3231443 (3 pages) | Cited 2 times

Online Publication Date: 17 September 2009

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A kind of inversion domains (IDs) which originated from the tips of threading dislocations were observed in the Al0.65Ga0.35N layer by transmission electron microscopy (TEM). The IDs showed columnar structures with diameters of 10–20 nm. We find that the dislocations evolved into V-shape boundaries then form IDs. By high resolution TEM analysis, the atomic structure at the boundary was proved to be the IDB∗ structure, in which each atom remains fourfold coordinated without the formation of Ga–Ga or N–N bonds.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.ag Semiconductors

Defect-free single-crystal Ge island arrays on insulator by rapid-melting-growth combined with seed-positioning technique

Kaoru Toko, Takashi Sakane, Takanori Tanaka, Taizoh Sadoh, and Masanobu Miyao

Appl. Phys. Lett. 95, 112107 (2009); http://dx.doi.org/10.1063/1.3231925 (3 pages) | Cited 9 times

Online Publication Date: 18 September 2009

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Single-crystal Ge island arrays on SiO2/Si structures are desired to merge advanced Ge devices into Si large scale integrated circuit (LSI). We have developed the rapid-melting-growth process of amorphous Ge by using Ni-imprint-induced Si (111) fine crystals ( ∼ 1 μmϕ) as the growth seed. Arrays of (111) oriented single-crystal Ge islands with device size ( ∼ 10 μmϕ) are uniformly fabricated on SiO2/Si substrates. The cross-sectional transmission electron microscopy observation reveals that Ge islands include no dislocation or stacking fault. This method opens up a possibility to achieve hybrid SiGe-LSI with multifunctions.
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81.10.Fq Growth from melts; zone melting and refining
61.72.Nn Stacking faults and other planar or extended defects

Time-resolved luminescence studies of proton-implanted GaN

A. Pinos, S. Marcinkevičius, M. Usman, and A. Hallén

Appl. Phys. Lett. 95, 112108 (2009); http://dx.doi.org/10.1063/1.3226108 (3 pages) | Cited 7 times

Online Publication Date: 18 September 2009

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Time-resolved photoluminescence measurements performed on proton implanted and annealed GaN layers have shown that carrier lifetime can be tuned over two orders of magnitude and, at implantation dose of 1×1015 cm−2, decreases down to a few picoseconds. With annealing at temperatures between 250 and 750 °C, carrier lifetime, contrary to electrical characteristics, is only slightly restored, indicating that electrical compensation and carrier dynamics are governed by different defects. Ga vacancies, free and bound at threading dislocations, are suggested as the most probable defects, responsible for electrical compensation and carrier lifetime quenching.
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78.55.Cr III-V semiconductors
78.47.jd Time resolved luminescence
61.72.Cc Kinetics of defect formation and annealing
61.72.jd Vacancies
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Spectroscopic study of V doped Hg0.018Cd0.981Mn0.001Te bulk crystals as near-infrared materials for optical applications

Yu. P. Gnatenko, P. M. Bukivskij, Yu. P. Piryatinski, I. O. Faryna, O. A. Shigiltchoff, and R. V. Gamernyk

Appl. Phys. Lett. 95, 112109 (2009); http://dx.doi.org/10.1063/1.3226670 (3 pages) | Cited 2 times

Online Publication Date: 18 September 2009

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It was shown that the photosensitivity region of the semi-insulating V doped Hg0.018Cd0.981Mn0.001Te crystals extends up to 1800 nm and is caused by the electron photogeneration resulting in the transitions from the main 4T1(F) state to the excited 4A2(F)- and 4T1(P) states of V2+ ions, which are in resonance with the conduction band. The electronic processes in the crystals are fast and correspond to the nanosecond region. Codoping by the Mn atoms leads to considerable improvement their optical quality and increase the resistivity. The obtained results indicate that such crystals can be considered as promising near-infrared materials for various optical applications.
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78.30.Er Solid metals and alloys
71.20.Gj Other metals and alloys
61.72.up Other materials

The reason for the increased threshold switching voltage of SiO2 doped Ge2Sb2Te5 thin films for phase change random access memory

Seung Wook Ryu, Jong Ho Lee, Young Bae Ahn, Choon Hwan Kim, Bong Seob Yang, Gun Hwan Kim, Soo Gil Kim, Se-Ho Lee, Cheol Seong Hwang, and Hyeong Joon Kim

Appl. Phys. Lett. 95, 112110 (2009); http://dx.doi.org/10.1063/1.3232237 (3 pages) | Cited 7 times

Online Publication Date: 18 September 2009

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This study examined the threshold switching voltage (VT) of 150 nm thick SiO2 doped Ge2Sb2Te5 (SGST) films for phase change random access memory applications. The VT of the SGST films increased from ∼ 0.9 V (for GST) to ∼ 1.5 V with increasing SiO2 content. The optical band gap and Urbach edge of the SGST films were similar regardless of the SiO2 concentration. The dielectric constant decreased by ∼ 37% and the electrical resistivity increased by ∼ 19%. The increase in VT of SGST films is associated with an effective increase in electric field and the decreased generation rate caused by impact ionization.
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85.30.-z Semiconductor devices
84.30.Sk Pulse and digital circuits
73.61.Le Other inorganic semiconductors
73.50.Fq High-field and nonlinear effects
77.22.Ch Permittivity (dielectric function)

Ferromagnetism in Cu-doped AlN films

Fan-Yong Ran, M. Subramanian, Masaki Tanemura, Yasuhiko Hayashi, and Takehiko Hihara

Appl. Phys. Lett. 95, 112111 (2009); http://dx.doi.org/10.1063/1.3232238 (3 pages) | Cited 10 times

Online Publication Date: 18 September 2009

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AlN films doped with 3.2–8.2 at. % Cu were deposited by helicon magnetron sputtering. The films exhibited ferromagnetism with a Curie temperature above 360 K. The observed magnetic anisotropy and exclusion of ferromagnetic contamination indicated that the ferromagnetism was the intrinsic property of Cu-doped AlN films. Room-temperature (RT) saturation magnetization (Ms) tended to decrease with increasing Cu concentration and the maximum RT Ms obtained was about 8.5 emu/cm3 (0.6 μB/Cu). Vacuum annealing increased the RT Ms values and meanwhile reduced ratio of N/(Al+Cu), which suggested that Al interstitial and N vacancy might contribute to the observed ferromagnetic behavior.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Pp Magnetic semiconductors
81.15.Cd Deposition by sputtering
68.55.ag Semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Gw Magnetic anisotropy
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Engineering double-shifted hysteresis loops in Co/IrMn/Cu/Co films

R. Cichelero, L. G. Pereira, T. Dias, J. E. Schmidt, C. Deranlot, F. Petroff, and J. Geshev

Appl. Phys. Lett. 95, 112501 (2009); http://dx.doi.org/10.1063/1.3227840 (3 pages) | Cited 3 times

Online Publication Date: 15 September 2009

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Co(3 nm)/IrMn(15 nm)/Cu(dCu)/Co(7 nm) films were subjected to magnetic annealing where its temperature and duration as well as the direction and amplitude of the applied field were varied. We demonstrate that the exchange-bias field magnitude and sign of the subloop of the bottom-pinned Co layer can be tailored in a controlled manner allowing the whole hysteresis loop to be tuned from a double negatively/negatively shifted to a double negatively/positively shifted with the shifts of the subloops in antiphase.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Et Exchange and superexchange interactions
75.60.Nt Magnetic annealing and temperature-hysteresis effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Wide range and tunable linear magnetic tunnel junction sensor using two exchange pinned electrodes

B. Negulescu, D. Lacour, F. Montaigne, A. Gerken, J. Paul, V. Spetter, J. Marien, C. Duret, and M. Hehn

Appl. Phys. Lett. 95, 112502 (2009); http://dx.doi.org/10.1063/1.3226676 (3 pages) | Cited 6 times

Online Publication Date: 16 September 2009

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A magnetic tunnel junction sensor with both the detection and the reference layers pinned by IrMn is fabricated. Using the differences in the blocking temperatures of the IrMn films with different thicknesses, crossed anisotropies can be induced between the detection and the reference electrodes. The pinning of the sensing electrode ensures a linear and reversible output. It also allows tuning both the sensitivity and the linear range of the sensor. The sensitivity varies linearly with the ferromagnetic thickness of the detection electrode. It is demonstrated that an increased thickness leads to a rise of sensitivity and a reduction of the operating range.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys
75.50.Ee Antiferromagnetics
75.30.Gw Magnetic anisotropy

Effect of the introduction of H atoms on magnetic properties and magnetic entropy change in metamagnetic Heusler alloys Ni–Mn–In

F. X. Hu, J. Wang, L. Chen, J. L. Zhao, J. R. Sun, and B. G. Shen

Appl. Phys. Lett. 95, 112503 (2009); http://dx.doi.org/10.1063/1.3229890 (3 pages) | Cited 2 times

Online Publication Date: 16 September 2009

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By hydrogen insertion into Ni51Mn49−xInx (x = 16.2,16.6) Heusler alloys, the interstitial compounds Ni51Mn49−xInxHδ were fabricated. The introduction of H atoms does not change the L21 structure of the alloys but shifts martensitic temperature (TM) to lower temperature. Magnetic measurements indicated the hydrogenated Ni51Mn49−xInxHδ compounds retain the metamagnetic properties although the ferromagnetic behavior of martensitic phases is slightly enhanced due to the introduction of H atoms. The strong metamagnetic behaviors result in large magnetocaloric effect (MCE). By controlling H content an extended temperature range having large MCE can be achieved.
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75.30.Sg Magnetocaloric effect, magnetic cooling
61.72.jj Interstitials
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
81.20.-n Methods of materials synthesis and materials processing
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.30.Kf Martensitic transformations
65.40.gd Entropy

Effect of biaxial strain on the electrical and magnetic properties of (001) La0.7Sr0.3MnO3 thin films

C. Adamo, X. Ke, H. Q. Wang, H. L. Xin, T. Heeg, M. E. Hawley, W. Zander, J. Schubert, P. Schiffer, D. A. Muller, L. Maritato, and D. G. Schlom

Appl. Phys. Lett. 95, 112504 (2009); http://dx.doi.org/10.1063/1.3213346 (3 pages) | Cited 30 times

Online Publication Date: 17 September 2009

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We have studied the effect of biaxial strain on thin films of (001) La0.7Sr0.3MnO3. We deposited films by reactive molecular-beam epitaxy on different single crystalline substrates, varying the substrate-induced biaxial strain from −2.3% to +3.2%. Magnetization and electrical transport measurements reveal that the dependence of the Curie temperature on biaxial strain is in very good agreement with the theoretical predictions of Millis et al. [J. Appl. Phys. 83, 1588 (1998) ].
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.aj Insulators
73.61.Ng Insulators
72.20.My Galvanomagnetic and other magnetotransport effects

Enhancement of the magnetotransport and magnetoresistive anisotropy in Sm0.55Sr0.45MnO3/Nd0.55Sr0.45MnO3 bilayers

M. Egilmez, M. Abdelhadi, Z. Salman, K. H. Chow, and J. Jung

Appl. Phys. Lett. 95, 112505 (2009); http://dx.doi.org/10.1063/1.3231441 (3 pages) | Cited 6 times

Online Publication Date: 17 September 2009

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In a sharp contrast to bulk Sm0.55Sr0.45MnO3 (SSMO) the SSMO films grown on LaAlO3 and SrTiO3 substrates exhibit insulating behavior with a negligible magnetoresistive effect. However, when these films are buffered by a thin layer of Nd0.55Sr0.45MnO3 a large low field magnetoresistance along with the bulklike properties are observed. These results are reproducible and suggest that the low field magnetoresistance and magnetoresistive anisotropy could be enhanced dramatically in multilayered manganite films. These changes are attributed to the differences in the strain states of these films.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.15.Cd Deposition by sputtering
75.70.Ak Magnetic properties of monolayers and thin films
75.47.Lx Magnetic oxides
75.30.Gw Magnetic anisotropy

Ab initio study of ferroelectric and nonlinear optical performance in BiFeO3 ultrathin films

Sheng Ju and Tian-Yi Cai

Appl. Phys. Lett. 95, 112506 (2009); http://dx.doi.org/10.1063/1.3232215 (3 pages) | Cited 2 times

Online Publication Date: 17 September 2009

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Density functional theory within the local density approximation plus on-site Coulomb repulsion is applied to investigate the crystal structure, electronic structure, multiferroism, linear, and nonlinear optical response in BiFeO3 ultrathin films, which are fabricated via epitaxial growth on (001)-oriented SrTiO3 substrates and have a strained P4mm phase. Born effective charges are calculated within the Berry-phase method and the spontaneous electric polarization is found to be 79 μC/cm2. The second-harmonic generation susceptibility, which can reach 7.5×10−7 esu, undergoes a substantial change between different magnetic orderings. Our calculations demonstrate the existence of robust ferroelectric distortion and nonlinear optical response in these ultrathin films.
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77.80.-e Ferroelectricity and antiferroelectricity
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
61.66.Fn Inorganic compounds
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
77.22.Ej Polarization and depolarization
71.20.Ps Other inorganic compounds
68.55.-a Thin film structure and morphology
78.66.Nk Insulators
77.55.-g Dielectric thin films
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