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19 Dec 2011

Volume 99, Issue 25, Articles (25xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 99, 253701 (2011); http://dx.doi.org/10.1063/1.3666819 (3 pages)

Jun Huang, Hui Li, Wei Chen, Guo-Hua Lv, Xing-Quan Wang, Guo-Ping Zhang, Kostya Ostrikov, Peng-Ye Wang, and Si-Ze Yang
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Catalyst-free growth of high-optical quality GaN nanowires by metal-organic vapor phase epitaxy

X. J. Chen, B. Gayral, D. Sam-Giao, C. Bougerol, C. Durand, and J. Eymery

Appl. Phys. Lett. 99, 251910 (2011); http://dx.doi.org/10.1063/1.3671365 (3 pages) | Cited 7 times

Online Publication Date: 22 December 2011

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Catalyst-free GaN wires with 100–200 nm diameters are grown on bare c-sapphire substrates by a metal-organic vapor phase epitaxy approach using both low V/III ratio and V-III precursor flows that favor a reaction-limited growth regime. The polarity control of the initial seeds allows obtaining pencil-shape wires with very sharp pyramids at their top (∼5 nm diameter). These defect-free nanowires evidence excellent structural and optical properties as shown by a sharp photoluminescence linewidth (1–3 meV at 5 K).
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.07.Gf Nanowires
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Optoelectronic behaviors and carrier dynamics of individual localized luminescent centers in InGaN quantum-well light emitting diodes

Suman De, Dibyendu Kumar Das, Arunasish Layek, Archana Raja, Manoj Kumar Singh, Arnab Bhattacharya, Subhabrata Dhar, and Arindam Chowdhury

Appl. Phys. Lett. 99, 251911 (2011); http://dx.doi.org/10.1063/1.3671092 (4 pages) | Cited 2 times

Online Publication Date: 23 December 2011

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Spatially, spectrally, and temporally resolved photoluminescence (PL) microscopy was performed on InGaN quantum-well light emitting diodes to probe individual localized luminescent centers arising from disorder induced potential fluctuations. Two energetically distinct localization centers were identified where the photoemission quantum-efficiency (QE) are correlated to the transition energies. PL lifetime measurements on emission centers suggest that activation barrier for non-radiative recombination (NR) processes determines their QE. The disparity in carrier dynamics not only substantiate two diverse mechanisms for localization processes, but also indicate the presence of multiple NR channels even within the trap centers implying their lateral dimensions to span several nanometers.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Interferometric scanning microscopy for the study of disordered materials

D. Kumar and M. M. J. Treacy

Appl. Phys. Lett. 99, 251912 (2011); http://dx.doi.org/10.1063/1.3671146 (4 pages)

Online Publication Date: 23 December 2011

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We demonstrate an interferometric optical technique that probes pair-pair correlations in disordered materials. Fraunhofer diffraction patterns, using coherent double-probe illumination, exhibit Young’s interference fringes whose strength is influenced by structural correlations between the two probed regions. Fourier transforms of diffraction patterns exhibit holographic sidebands, and the strength of correlations is proportional to the sideband intensity. Autoregression analysis of the correlation strength provides a direct measure of the characteristic ordering length scales. This technique is extendable in principle to x-ray and electron probes for studying materials at atomic length scales.
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61.41.+e Polymers, elastomers, and plastics

Nucleation and propagation of voids in microbumps for 3 dimensional integrated circuits

Hsueh-Hsien Hsu, Shin-Yi Huang, Tao-Chih Chang, and Albert T. Wu

Appl. Phys. Lett. 99, 251913 (2011); http://dx.doi.org/10.1063/1.3671391 (3 pages) | Cited 1 time

Online Publication Date: 23 December 2011

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The shrinking solder dimensions greatly impact the reliability of devices and increase entire failure modes. Limited solder volumes can be consumed completely and transformed into intermetallic compound (IMC) microbumps. Microvoids surface when microbumps are formed and may be attributed to a mismatch of the thermal expansion coefficient between the constituents. After thermal aging at 150 °C, the stress induced by the growth of IMCs relaxes and enhances propagation of the cracks along the middle of the bumps. The brittle nature of the IMC showed minimal resistance to cracks and incurred a failure mode.
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85.40.Ls Metallization, contacts, interconnects; device isolation
62.20.mj Brittleness
62.20.mt Cracks
61.72.Qq Microscopic defects (voids, inclusions, etc.)
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Controlling split-ring resonators with light

Polina V. Kapitanova, Stanislav I. Maslovski, Ilya V. Shadrivov, Pavel M. Voroshilov, Dmitry S. Filonov, Pavel A. Belov, and Yuri S. Kivshar

Appl. Phys. Lett. 99, 251914 (2011); http://dx.doi.org/10.1063/1.3671617 (3 pages) | Cited 5 times

Online Publication Date: 23 December 2011

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We propose an original approach for creating tunable electromagnetic metamaterials. We demonstrate experimentally that magnetic resonance of a split-ring resonator (“meta-atom” of a composite material) with a photodiode operated in photovoltaic mode can be tuned by changing the intensity of an external light source. Moreover, for two coupled resonators, we show that we can achieve light-induced switching between dark- and bright-mode responses.
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42.79.-e Optical elements, devices, and systems
85.60.Dw Photodiodes; phototransistors; photoresistors
42.70.-a Optical materials
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Metal-oxide-oxide-metal granular tunnel diodes fabricated by anodization

Wenbin Fan, Melissa Commisso Dolph, Jiwei Lu, and Stuart A. Wolf

Appl. Phys. Lett. 99, 252101 (2011); http://dx.doi.org/10.1063/1.3670057 (3 pages)

Online Publication Date: 19 December 2011

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A metal-oxide-oxide-metal (MO-OM) junction was fabricated based on anodized Al and Ta granular metal-oxide tunnel junctions. Electrical transport properties of the MO-OM junction were investigated at various temperatures. A strong asymmetric nonlinear current-voltage curve at room temperature indicated a diode-like behavior with a threshold voltage of 0.19 V under forward bias. The nonlinear current-voltage curves under forward and reverse biases were well fitted separately by the Simmons equation (J. G. Simmons, J. Appl. Phys. 34, 1793 (1963)) with barrier thickness, height, and tunneling area treated as variables.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
81.65.-b Surface treatments

Dependence of spontaneous polarization on stacking sequence in SiC revealed by local Schottky barrier height variations over a partially formed 8H-SiC layer on a 4H-SiC substrate

Kibog Park, Heung Seok Go, Youngeun Jeon, Jonathan P. Pelz, Xuan Zhang, and Marek Skowronski

Appl. Phys. Lett. 99, 252102 (2011); http://dx.doi.org/10.1063/1.3670329 (4 pages)

Online Publication Date: 19 December 2011

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Ballistic electron emission microscopy was used to measure the increase of local Schottky barrier (compared to the surrounding 4H-SiC area) over a partial 8H-SiC layer that is the surface-exposed tail of an 8H stacking fault inclusion extending from 4H substrate. This local increase is believed to be due to polarization charge induced at the interface of partial 8H layer and underlying 4H host, resulting from the spontaneous polarization (SP) difference between SiC regions with different bilayer stacking. This is a direct experimental probe of the dependence of SP in SiC on local stacking sequence by measuring carrier transport.
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77.22.Ej Polarization and depolarization
61.72.Nn Stacking faults and other planar or extended defects
61.72.Qq Microscopic defects (voids, inclusions, etc.)
73.30.+y Surface double layers, Schottky barriers, and work functions
73.61.Le Other inorganic semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Analysis of hysteresis characteristics of silicon nanowire biosensors in aqueous environment

Hyeri Jang, Jieun Lee, Jung Han Lee, Sungmin Seo, Byung-Gook Park, Dong Myong Kim, Dae Hwan Kim, and In-Young Chung

Appl. Phys. Lett. 99, 252103 (2011); http://dx.doi.org/10.1063/1.3669409 (3 pages) | Cited 1 time

Online Publication Date: 20 December 2011

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The hysteresis phenomenon has been widely observed in transfer characteristics of silicon nanowire (SiNW) biosensor devices in aqueous environment. Considering the experimental observation in the change of the liquid potential due to the charge flow through the oxide layer, we build up an electrical model for the biosensor system with the solution, SiNW, dielectric oxide, and the back-gated substrate, and investigate the hysteresis behavior based on the model.
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87.85.Rs Nanotechnologies-applications
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
87.85.Ox Biomedical instrumentation and transducers, including micro-electro-mechanical systems (MEMS)

Impact of fixed charge on metal-insulator-semiconductor barrier height reduction

Jenny Hu, Aneesh Nainani, Yun Sun, Krishna C. Saraswat, and H.-S. Philip Wong

Appl. Phys. Lett. 99, 252104 (2011); http://dx.doi.org/10.1063/1.3669414 (4 pages) | Cited 2 times

Online Publication Date: 20 December 2011

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Recently, the insertion of ultrathin insulators to form metal-insulator-semiconductor (MIS) contacts has been used extensively to reduce the Schottky barrier height and to shift the Fermi level pinning. In this paper, we investigate the physical non-idealities of the ultrathin insulator in Al/Al2O3/n-GaAs MIS through stoichiometry, density, and bandgap measurements. These structural non-idealities electrically manifest as bulk and interface fixed charges that are found to contribute to the observed barrier height reduction. The effect of fixed charge has not been considered before, and when combined with the previously reported interface dipoles, it provides a more thorough understanding of the MIS contacts.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.30.+y Surface double layers, Schottky barriers, and work functions
61.66.Bi Elemental solids
61.66.Dk Alloys

Persistent ion beam induced conductivity in zinc oxide nanowires

Andreas Johannes, Raphael Niepelt, Martin Gnauck, and Carsten Ronning

Appl. Phys. Lett. 99, 252105 (2011); http://dx.doi.org/10.1063/1.3671164 (3 pages) | Cited 1 time

Online Publication Date: 21 December 2011

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We report persistently increased conduction in ZnO nanowires irradiated by ion beam with various ion energies and species. This effect is shown to be related to the already known persistent photo conduction in ZnO and dubbed persistent ion beam induced conduction. Both effects show similar excitation efficiency, decay rates, and chemical sensitivity. Persistent ion beam induced conduction will potentially allow countable (i.e., single dopant) implantation in ZnO nanostructures and other materials showing persistent photo conduction.
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73.61.Ga II-VI semiconductors
66.30.H- Self-diffusion and ionic conduction in nonmetals
61.80.Jh Ion radiation effects
72.40.+w Photoconduction and photovoltaic effects

Predictive circuit model for noise in quantum cascade detectors

A. Delga, M. Carras, L. Doyennette, V. Trinité, A. Nedelcu, and V. Berger

Appl. Phys. Lett. 99, 252106 (2011); http://dx.doi.org/10.1063/1.3671328 (3 pages) | Cited 4 times

Online Publication Date: 21 December 2011

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Electronic noise in quantum cascade structures is investigated theoretically and experimentally under dark conditions. A model based on a unified and insightful vision of noise generating mechanisms is proposed and describes both thermal and shot noise behaviors. Dark measurements of quantum cascade detectors operating at 8 μm and 15 μm are retrieved with good quantitative agreement. This model is expected to be applicable to other quantum structures and under illumination.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

Domain wall conductivity in oxygen deficient multiferroic YMnO3 single crystals

Y. Du, X. L. Wang, D. P. Chen, S. X. Dou, Z. X. Cheng, M. Higgins, G. Wallace, and J. Y. Wang

Appl. Phys. Lett. 99, 252107 (2011); http://dx.doi.org/10.1063/1.3671393 (4 pages) | Cited 1 time

Online Publication Date: 22 December 2011

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The transport properties of domain walls in oxygen deficient multiferroic YMnO3 single crystals have been probed using conductive atomic force microscopy and piezoresponse force microscopy. Domain walls exhibit significantly enhanced conductance after being poled in electric fields, possibly induced by oxygen vacancy ordering at domain walls. The electronic conduction can be understood by the Schottky emission and Fowler-Nordheim tunnelling mechanisms. Our results show that the domain wall conductance can be modulated through band structure engineering by manipulating ordered oxygen vacancies in the poling fields.
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77.80.Dj Domain structure; hysteresis
61.72.jd Vacancies
75.85.+t Magnetoelectric effects, multiferroics
71.20.Ps Other inorganic compounds
73.40.Gk Tunneling
77.22.Ej Polarization and depolarization
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X-ray magnetic circular dichroism of ferromagnetic Co4N epitaxial films on SrTiO3(001) substrates grown by molecular beam epitaxy

Keita Ito, Kazunori Harada, Kaoru Toko, Mao Ye, Akio Kimura, Yukiharu Takeda, Yuji Saitoh, Hiro Akinaga, and Takashi Suemasu

Appl. Phys. Lett. 99, 252501 (2011); http://dx.doi.org/10.1063/1.3670353 (3 pages) | Cited 3 times

Online Publication Date: 19 December 2011

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5-nm thick Co4N layers capped with 3-nm thick Au layers were grown epitaxially on SrTiO3(001) substrates by molecular beam epitaxy using solid Co and a radio-frequency NH3 plasma. Spin and orbital magnetic moments of the Co4N layers were estimated using x-ray magnetic circular dichroism (XMCD) measurements at 300 K. The site-averaged Co 3d spin magnetic moment is evaluated to be about 1.4 μB, which is smaller than that predicted theoretically (1.58 μB). The element-specific XMCD intensities for the Co L3 edge and N K edge show that the magnetic moment is induced at the N atoms.
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78.20.Ls Magneto-optical effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.55.aj Insulators
75.50.Dd Nonmetallic ferromagnetic materials

Correlation between the ferromagnetic metal percolation and the sign evolution of angular dependent magnetoresistance in Pr0.7Ca0.3MnO3 film

Y. Q. Zhang, H. Meng, X. W. Wang, J. J. Liu, J. Du, and Z. D. Zhang

Appl. Phys. Lett. 99, 252502 (2011); http://dx.doi.org/10.1063/1.3670399 (4 pages)

Online Publication Date: 20 December 2011

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Angular dependent magnetoresistance (AMR) phenomena in Pr0.7Ca0.3MnO3 film have been investigated. A transition between cos2θ dependent AMR in an insulating state at low fields and sin2θ dependent AMR in a metal state at high fields is observed at intermediate fields, depending on the temperature and/or strength of an applied magnetic field. Although the AMR sign evolution process from cos2θ dependence to sin2θ dependence at low temperature is different from that at high temperature due to existence of ferromagnetic insulator besides charge ordering antiferromagnetic insulator, we believe that such AMR sign evolutions are closely related with magnetic-field-induced ferromagnetic metal percolation behavior.
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72.20.My Galvanomagnetic and other magnetotransport effects
75.50.Ee Antiferromagnetics
75.70.-i Magnetic properties of thin films, surfaces, and interfaces

(001) textured L10-FePt pseudo spin valve with TiN spacer

P. Ho, G. C. Han, K. H. He, G. M. Chow, and J. S. Chen

Appl. Phys. Lett. 99, 252503 (2011); http://dx.doi.org/10.1063/1.3671988 (4 pages) | Cited 2 times

Online Publication Date: 21 December 2011

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TiN was investigated as a potential spacer material in L10-FePt based pseudo spin valves (PSV). PSVs with the structure MgO/L10-Fe50Pt50 (20 nm)/TiN (5 nm)/L10-Fe50Pt50 (x nm) were fabricated, where x was varied from 5 to 20 nm. The highest giant magnetoresistance (GMR) ratio of 0.61% was obtained for the PSV with a top L10-FePt thickness of 20 nm. Contributions to the GMR arose from both the spin dependent scattering at the FePt/TiN interfaces and domain wall resistivity. Magnon magnetoresistance was also observed in the fabricated PSVs.
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75.47.De Giant magnetoresistance
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.15.Cd Deposition by sputtering
75.60.Ch Domain walls and domain structure
68.55.-a Thin film structure and morphology

Unusual magnetic anisotropy in the ferromagnetic shape-memory alloy Ni50Fe23Ga27

J. F. Qian (钱金凤), E. K. Liu (刘恩克), L. Feng (冯琳), W. Zhu (朱伟), G. J. Li (李贵江), W. H. Wang (王文洪), G. H. Wu (吴光恒), Z. W. Du (杜志伟), and X. Fu (付新)

Appl. Phys. Lett. 99, 252504 (2011); http://dx.doi.org/10.1063/1.3671666 (3 pages)

Online Publication Date: 21 December 2011

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Unusual magnetic anisotropy of the ferromagnetic shape-memory alloy Ni50Fe23Ga27 has been observed. The anisotropy of the austenite becomes very large, even larger than that of the martensite in ribbon samples. Lowering the temperature from 300 K to 80 K, the saturation field of the austenite is dramatically increased from 200 Oe up to 6 kOe. This high-anisotropy behavior clearly highlights the demagnetization effect of the martensitic transformation. The physical mechanism is attributed to a collective effect coming from the atomic disorder, the premartensitic transformation, and the off-stoichiometric Ga-rich composition of the alloys.
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75.30.Gw Magnetic anisotropy
75.50.Bb Fe and its alloys
75.60.-d Domain effects, magnetization curves, and hysteresis
81.30.Kf Martensitic transformations
64.70.kd Metals and alloys
61.66.Bi Elemental solids
61.66.Dk Alloys

Observations of laser induced magnetization dynamics in Co/Pd multilayers with coherent x-ray scattering

B. Wu, D. Zhu, Y. Acremann, T. A. Miller, A. M. Lindenberg, O. Hellwig, J. Stöhr, and A. Scherz

Appl. Phys. Lett. 99, 252505 (2011); http://dx.doi.org/10.1063/1.3670305 (3 pages) | Cited 2 times

Online Publication Date: 22 December 2011

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We report on time-resolved coherent x-ray scattering experiments of laser induced magnetization dynamics in Co/Pd multilayers with a high repetition rate optical pump x-ray probe setup. Starting from a multi-domain ground state, the magnetization is uniformly reduced after excitation by an intense 50 fs laser pulse. Using the normalized time correlation, we study the magnetization recovery on a picosecond timescale. The dynamic scattering intensity is separated into an elastic portion at length scales above 65 nm, which retains memory of the initial domain magnetization, and a fluctuating portion at smaller length scales corresponding to domain boundary motion during recovery.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
78.20.Ls Magneto-optical effects
75.78.Fg Dynamics of domain structures
75.60.Ch Domain walls and domain structure
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.70.Ck X-ray scattering

Large coercivity in nanostructured rare-earth-free MnxGa films

T. J. Nummy, S. P Bennett, T. Cardinal, and D. Heiman

Appl. Phys. Lett. 99, 252506 (2011); http://dx.doi.org/10.1063/1.3671329 (3 pages) | Cited 6 times

Online Publication Date: 22 December 2011

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The magnetic hysteresis of MnxGa films exhibit remarkably large coercive fields as high as μoHC = 2.5 T when fabricated with nanoscale particles of a suitable size and orientation. This coercivity is an order of magnitude larger than in well-ordered epitaxial film counterparts and bulk materials. The enhanced coercivity is attributed to the combination of large magnetocrystalline anisotropy and ∼50-100 nm size nanoparticles. The large coercivity is also replicated in the electrical properties through the anomalous Hall effect. The magnitude of the coercivity approaches that found in rare-earth magnets, making them attractive for rare-earth-free magnet applications.
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75.70.-i Magnetic properties of thin films, surfaces, and interfaces
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.22.-f Electronic structure of nanoscale materials and related systems
75.30.Gw Magnetic anisotropy
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Origin of the collapse of tunnel magnetoresistance at high annealing temperature in CoFeB/MgO perpendicular magnetic tunnel junctions

H. D. Gan, H. Sato, M. Yamanouchi, S. Ikeda, K. Miura, R. Koizumi, F. Matsukura, and H. Ohno

Appl. Phys. Lett. 99, 252507 (2011); http://dx.doi.org/10.1063/1.3671669 (3 pages) | Cited 4 times

Online Publication Date: 23 December 2011

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We have investigated a tunnel magnetoresistance (TMR) ratio of CoFeB/MgO perpendicular magnetic tunnel junctions (p-MTJs) with a 40 nm diameter as a function of an annealing temperature Ta. The TMR ratio at room temperature (RT) increases with increasing Ta and reaches 149% at Ta = 350 °C, and further increase of Ta results in a strong reduction of the TMR ratio, i.e., 2% at Ta = 400 °C. The temperature dependence of the junction resistance versus magnetic field loops reveals that the reduced TMR ratio at RT is due to the disappearance of a stable antiparallel magnetization configuration. We find that reduction of dipole coupling restores the TMR ratio.
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75.47.Pq Other materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.40.Gh Other heat and thermomechanical treatments
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Anomalous elastic behavior of relaxor ferroelectric Ca0.28Ba0.72Nb2O6:Ce studied by resonant ultrasound spectroscopy

Chandra Shekhar Pandey, Jürgen Schreuer, Manfred Burianek, and Manfred Mühlberg

Appl. Phys. Lett. 99, 252901 (2011); http://dx.doi.org/10.1063/1.3670323 (3 pages) | Cited 3 times

Online Publication Date: 19 December 2011

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Elastic behavior of tetragonal tungsten bronze uniaxial relaxor ferroelectric cerium doped Ca0.28Ba0.72Nb2O6 single crystal was investigated employing resonant ultrasound spectroscopy in the temperature range from room temperature up to 1323 K. Doping of cerium lowers the phase transition temperature Tc and Burns temperature Tb significantly, however, intermediate characteristic temperature T* (between the Burns temperature Tb and the temperature of maximum dielectric permittivity Tm) remains same as for pure Ca0.28Ba0.72Nb2O6. All independent elastic constants evolved differently with temperature, reflecting their coupling to different types of the reorientational motion of the polar nanoregions through their interaction with the acoustic waves.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.dq Other elastic constants
77.80.Jk Relaxor ferroelectrics
65.40.De Thermal expansion; thermomechanical effects
77.84.Ek Niobates and tantalates
77.22.Ch Permittivity (dielectric function)

In situ microwave characterization of microwire composites under mechanical stress

Faxiang Qin, C. Brosseau, and H. X. Peng

Appl. Phys. Lett. 99, 252902 (2011); http://dx.doi.org/10.1063/1.3668109 (4 pages) | Cited 4 times

Online Publication Date: 20 December 2011

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We present results of an experimental characterization of the dielectric properties and microwave absorption of rubber composite samples containing Fe4Co68.7Ni1B13Si11Mo2.3 amorphous microwires which are submitted to a low uniaxial tension. Measurements of the dielectric loss and microwave absorption as a function of strain over the frequency range of 300 MHz-6 GHz reveal that the uniaxial elongation randomly breaks wires at about 2.8% strain and this has for effect to decrease the loss factor for larger strain. Two possible mechanisms are identified to account for our observations, namely, the stress and shape effects. The ability to control this stretch breaking phenomenon will be instrumental to developing stress tunable microwire composites for sensing applications.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.43.Fs Glasses
75.50.Kj Amorphous and quasicrystalline magnetic materials
77.22.Gm Dielectric loss and relaxation

Electrical creep induced ferroelectric domain wall motion in BaTiO3 single crystal

Q. D. Liu and J. E. Huber

Appl. Phys. Lett. 99, 252903 (2011); http://dx.doi.org/10.1063/1.3671327 (3 pages)

Online Publication Date: 21 December 2011

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Observations of 180° domain patterns were made on a bulk BaTiO3 single crystal using atomic force microscopy and piezoresponse force microscopy (PFM). Surface electrodes were then used to apply a weak in-plane electric field, and in-situ measurements of electrical creep induced domain structure evolution were made. The out-of-plane electric field component presented by electrodes was insufficient to cause significant switching alone. However, in the presence of the scanning PFM tip, a gradual change in 180° domain configuration was observed. This suggests that by combining in-plane fields with an out-of plane bias, domain configurations can be manipulated at the surface of bulk crystals using low voltages.
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77.80.Dj Domain structure; hysteresis

Misfit strain dependence of ferroelectric and piezoelectric properties of clamped (001) epitaxial Pb(Zr0.52,Ti0.48)O3 thin films

Minh D. Nguyen, Matthijn Dekkers, Evert Houwman, Ruud Steenwelle, Xin Wan, Andreas Roelofs, Thorsten Schmitz-Kempen, and Guus Rijnders

Appl. Phys. Lett. 99, 252904 (2011); http://dx.doi.org/10.1063/1.3669527 (4 pages) | Cited 8 times

Online Publication Date: 22 December 2011

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A study on the effects of the residual strain in Pb(Zr0.52Ti0.48)O3 (PZT) thin films on the ferroelectric and piezoelectric properties is presented. Epitaxial (001)-oriented PZT thin film capacitors are sandwiched between SrRuO3 electrodes. The thin film stacks are grown on different substrate-buffer-layer combinations by pulsed laser deposition. Compressive or tensile strain caused by the difference in thermal expansion of the PZT film and substrate influences the ferroelectric and piezoelectric properties. All the PZT stacks show ferroelectric and piezoelectric behavior that is consistent with the theoretical model for strained thin films in the ferroelectric r-phase. We conclude that clamped (001) oriented Pb(Zr0.52Ti0.48)O3 thin films strained by the substrate always show rotation of the polarization vector.
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84.32.Tt Capacitors
77.84.Cg PZT ceramics and other titanates
77.55.Px Epitaxial and superlattice films
77.22.Ej Polarization and depolarization
77.80.-e Ferroelectricity and antiferroelectricity
81.15.Fg Pulsed laser ablation deposition

Ferroelectric and electrical characterization of multiferroic BiFeO3 at the single nanoparticle level

R. K. Vasudevan, K. A. Bogle, A. Kumar, S. Jesse, R. Magaraggia, R. Stamps, S. B. Ogale, H. S. Potdar, and V. Nagarajan

Appl. Phys. Lett. 99, 252905 (2011); http://dx.doi.org/10.1063/1.3671392 (4 pages) | Cited 5 times

Online Publication Date: 22 December 2011

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Ferroelectric BiFeO3 (BFO) nanoparticles deposited on epitaxial substrates of SrRuO3 (SRO) and La1−xSrxMnO3 (LSMO) were studied using band excitation piezoresponse spectroscopy (BEPS), piezoresponse force microscopy (PFM), and ferromagnetic resonance (FMR). BEPS confirms that the nanoparticles are ferroelectric in nature. Switching behavior of nanoparticle clusters were studied and showed evidence for inhomogeneous switching. The dimensionality of domains within nanoparticles was found to be fractal in nature, with a dimensionality constant of ∼1.4, on par with ferroelectric BFO thin-films under 100 nm in thickness. Ferromagnetic resonance studies indicate BFO nanoparticles only weakly affect the magnetic response of LSMO.
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77.55.F- High-permittivity capacitive films
73.22.-f Electronic structure of nanoscale materials and related systems
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
77.80.-e Ferroelectricity and antiferroelectricity
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
77.55.Nv Multiferroic/magnetoelectric films
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A thin film broadband absorber based on multi-sized nanoantennas

Yanxia Cui, Jun Xu, Kin Hung Fung, Yi Jin, Anil Kumar, Sailing He, and Nicholas X. Fang

Appl. Phys. Lett. 99, 253101 (2011); http://dx.doi.org/10.1063/1.3672002 (4 pages) | Cited 10 times

Online Publication Date: 19 December 2011

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We experimentally demonstrate an infrared broadband absorber based on an array of nanostrip antennas of several different sizes. The broadband property is due to the collective effect of magnetic responses excited by these nanoantennas at distinct wavelengths. By manipulating the differences of the nanostrip widths, the measured spectra clearly validate our design for the purpose of broadening the absorption band.
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84.40.Ba Antennas: theory, components and accessories
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