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26 Mar 2012

Volume 100, Issue 13, Articles (13xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 133701 (2012); http://dx.doi.org/10.1063/1.3696019 (3 pages)

Hewei Liu, Feng Chen, Qing Yang, Pubo Qu, Shengguan He, Xianhua Wang, Jinhai Si, and Xun Hou
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High-stiffness driven micromechanical resonators with enhanced power handling

Li-Jen Hou and Sheng-Shian Li

Appl. Phys. Lett. 100, 131908 (2012); http://dx.doi.org/10.1063/1.3698361 (3 pages)

Online Publication Date: 30 March 2012

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A two-port silicon-based micromechanical beam resonator driven at its high-stiffness locations has been proposed with enhanced power handling as compared with the same resonator but using conventional drive/sense configurations. The key to attaining superior power handling relies on the electrode arrangements where critical handling power (or Duffing-nonlinear bifurcation power) becomes much higher by driving the resonator at its high-stiffness locations than low-stiffness areas. In this work, resonators using high-stiffness driving approach exhibit around 20× (20 times) power handling improvement as compared to low-stiffness driving counterpart while the motional impedances in both cases are the same under linear operation.
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07.10.Cm Micromechanical devices and systems

Direction switching and beam steering of cholesteric liquid crystal gratings

Hung-Chang Jau, Tsung-Hsien Lin, Yan-Yu Chen, Chun-Wei Chen, Jui-Hsiang Liu, and Andy Y.-G. Fuh

Appl. Phys. Lett. 100, 131909 (2012); http://dx.doi.org/10.1063/1.3698384 (3 pages) | Cited 3 times

Online Publication Date: 30 March 2012

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This work proposes two mechanisms for switching the direction of stripes in cholesteric liquid crystal (CLC) gratings. The stripe direction depends on the ratio of cell gap to the natural pitch length (d/P0) of a CLC sample. Electrical switching is based on the different pitches at the planar and the transient planar states. Optical switching, however, changes pitch by using the photo-isomerization effect of the azobenzene doped in a CLC sample. Using the two mechanisms, we can switch the stripe directions in two orthogonal directions. Furthermore, the beam-steering capability of CLC gratings also remains effective after switching directions.
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42.70.Df Liquid crystals
42.79.Dj Gratings
42.79.Kr Display devices, liquid-crystal devices
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Non-Onsager mechanism of long-wave photogeneration in amorphous selenium at high electric fields

A. Reznik, K. Jandieri, F. Gebhard, and S. D. Baranovskii

Appl. Phys. Lett. 100, 132101 (2012); http://dx.doi.org/10.1063/1.3697643 (4 pages)

Online Publication Date: 26 March 2012

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The quantum efficiency of the free-carrier-photogeneration in amorphous selenium avalanche blocking structures is studied experimentally in a wide range of wavelengths (380–600 nm) at high electric fields (10−112.5Vμm−1). While at comparatively small excitation wavelengths (up to ≃ 540nm), our experimental results are consistent with the Onsager theory of electron-hole pair dissociation [L. Onsager, Phys. Rev. 54, 554 (1938)], at larger wavelengths (540–600 nm) and high electric fields Onsager theory fails to explain our results. The reason for the failure of the Onsager approach is discussed and an alternative theoretical tool is adopted to account for the experimental observations.
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72.40.+w Photoconduction and photovoltaic effects
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

The origin of non-Drude terahertz conductivity in nanomaterials

K. Shimakawa, T. Itoh, H. Naito, and S. O. Kasap

Appl. Phys. Lett. 100, 132102 (2012); http://dx.doi.org/10.1063/1.3697404 (3 pages) | Cited 6 times

Online Publication Date: 27 March 2012

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The Drude-Smith (DS) model hitherto has been a well accepted model for the terahertz conductivity of nanomaterials, even though its physical basis is not clear. It is shown that a series sequence of transport involving grains and grain boundaries produces a Lorentzian-type energy loss and dominates the THz conductivity in nanomaterials, which is able to explain both the real and imaginary parts of the conductivity. The present model represents a completely different point of view than the standard Drude-Smith model.
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78.70.Gq Microwave and radio-frequency interactions
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
81.05.Cy Elemental semiconductors
81.05.Hd Other semiconductors
61.72.Mm Grain and twin boundaries

Electron-nuclei spin coupling in GaAs—Free versus localized electrons

J. Huang, Y. S. Chen, A. Ludwig, D. Reuter, A. D. Wieck, and G. Bacher

Appl. Phys. Lett. 100, 132103 (2012); http://dx.doi.org/10.1063/1.3699261 (4 pages)

Online Publication Date: 27 March 2012

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We report on an experimental evidence of a significantly different dynamic nuclear polarization (DNP) for localized and itinerant electrons in n-GaAs. Optically injected spin-polarized electrons are used to generate dynamic nuclear polarization via electron-nucleus hyperfine interaction. Using time resolved Kerr rotation measurements for probing the transient Overhauser field, the DNP time constants for itinerant and localized electrons are extracted to be 10 min and less than 1 min, respectively. This is attributed to a rapid DNP occurring in the vicinity of the donors followed by a delayed nuclear spin polarization in between the donor sites.
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71.70.Jp Nuclear states and interactions
76.70.Fz Double nuclear magnetic resonance (DNMR), dynamical nuclear polarization
78.20.Jq Electro-optical effects
78.47.D- Time resolved spectroscopy (>1 psec)

Analysis of the reverse leakage current in AlGaN/GaN Schottky barrier diodes treated with fluorine plasma

Woo Jin Ha, Sameer Chhajed, Seung Jae Oh, Sunyong Hwang, Jong Kyu Kim, Jae-Hoon Lee, and Ki-Se Kim

Appl. Phys. Lett. 100, 132104 (2012); http://dx.doi.org/10.1063/1.3697684 (4 pages) | Cited 2 times

Online Publication Date: 27 March 2012

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The carrier transport mechanism of CF4 plasma-treated AlGaN/GaN Schottky barrier diodes (SBDs) under reverse bias is investigated. The reverse leakage current is reduced by ∼2 orders of magnitude after the CF4 plasma treatment, but increases exponentially with increasing temperature, indicating that a thermally activated transport mechanism is involved. Based on the activation energy estimated from temperature-dependent current-voltage characteristics and the emission barrier height extracted from Frenkel-Poole emission model, it is suggested that the dominant carrier transport mechanism in the CF4 plasma treated SBDs is the Frenkel-Poole emission from fluorine-related deep-level states into the continuum states of dislocations.
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85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices
52.77.-j Plasma applications

Polarization-induced remote interfacial charge scattering in Al2O3/AlGaN/GaN double heterojunction high electron mobility transistors

Dong Ji, Bing Liu, Yanwu Lu, Guipeng Liu, Qinsheng Zhu, and Zhanguo Wang

Appl. Phys. Lett. 100, 132105 (2012); http://dx.doi.org/10.1063/1.3698391 (4 pages) | Cited 3 times

Online Publication Date: 28 March 2012

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This study investigated on polarization-induced remote interfacial charge scattering, a scattering mechanism caused by the interfacial polarization charge, for Al2O3/AlGaN/GaN double heterojunction high electron mobility transistors (HEMTs). Results show that remote interfacial charge scattering plays a critical role in the mobility of two-dimensional electron gas (2DEG) in thin barrier HEMTs. The electronic mobility limited by remote charge scattering is found to be a function of the fixed charge density induced by the Al2O3 layer, 2DEG density, and barrier thickness. Results of this study can be used in designing structures to generate higher electron mobility in Al2O3/AlGaN/GaN double heterojunction HEMTs.
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85.30.Tv Field effect devices

Photoinduced modification of surface states in nanoporous InP

J. Lloyd-Hughes, S. Müller, G. Scalari, H. Bishop, A. Crossley, M. Enachi, L. Sirbu, and I. M. Tiginyanu

Appl. Phys. Lett. 100, 132106 (2012); http://dx.doi.org/10.1063/1.3697410 (3 pages) | Cited 2 times

Online Publication Date: 29 March 2012

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Porous honeycombs of n-type InP were investigated by terahertz time-domain and x-ray photoemission spectroscopies. After photoexcitation the dark conductivity was found to increase quasi-irreversibly, recovering only after several hours in air. The calculated electron density for different surface pinning energies suggests that photoexcitation may reduce the density of surface states.
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73.20.At Surface states, band structure, electron density of states
78.70.Gq Microwave and radio-frequency interactions
72.80.Ey III-V and II-VI semiconductors
78.67.Rb Nanoporous materials
72.40.+w Photoconduction and photovoltaic effects
79.60.Jv Interfaces; heterostructures; nanostructures

Anharmonic vibrations of the dicarbon antisite defect in 4H-SiC

F. Yan, R. P. Devaty, W. J. Choyke, A. Gali, T. Kimoto, T. Ohshima, and G. Pensl

Appl. Phys. Lett. 100, 132107 (2012); http://dx.doi.org/10.1063/1.3699269 (3 pages) | Cited 2 times

Online Publication Date: 29 March 2012

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Dicarbon antisite defects were created by either electron irradiation or ion implantation into 4H-SiC. The no-phonon lines from the dicarbon antisite defect center were observed with their phonon replicas. The stretch frequencies of the defect were observed up to the fifth harmonic. The Morse potential model accounts for the anharmonicity quite well and gives a very good prediction of the vibration energies up to the fifth harmonic with an error of less than 1%. First principles calculations show that the model of a dicarbon antisite defect along with its four nearest neighboring carbon atoms can explain the observed anharmonicity.
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63.20.Ry Anharmonic lattice modes
78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors
61.72.up Other materials
61.80.Fe Electron and positron radiation effects
61.82.Fk Semiconductors

Tuning minority-carrier lifetime through stacking fault defects: The case of polytypic SiC

Bin Chen, Hirofumi Matsuhata, Takashi Sekiguchi, Akimasa Kinoshita, Kyouichi Ichinoseki, and Hajime Okumura

Appl. Phys. Lett. 100, 132108 (2012); http://dx.doi.org/10.1063/1.3700963 (4 pages) | Cited 1 time

Online Publication Date: 30 March 2012

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Minority-carrier lifetime is one of the key parameters governing the performance of semiconductor devices. Here, we report on tuning the minority-carrier lifetime through stacking fault (SF) defects in polytypic SiC. The SFs are distinguished in terms of their characteristic luminescence peaks at 482 nm, 471 nm, and 417 nm, respectively. Different from general point, linear, and volume defects, the planar SFs demonstrate the interesting phenomena of either decreasing or increasing the minority-carrier lifetime, which depend on the SF-related energy levels. The mechanism for the down/up modulation of the carrier lifetime through the SFs is discussed.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.72.Nn Stacking faults and other planar or extended defects
78.60.Hk Cathodoluminescence, ionoluminescence

Epitaxial growth of thin films and nanodots of ZnO on Si(111) by pulsed laser deposition

Sung Kyun Lee and Jong Yeog Son

Appl. Phys. Lett. 100, 132109 (2012); http://dx.doi.org/10.1063/1.3698470 (4 pages) | Cited 1 time

Online Publication Date: 30 March 2012

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Epitaxial (0001) ZnO thin films were grown on (111) Si substrates buffered with intermediate epitaxial (111) yttria-stabilized zirconia (YSZ) layers by pulsed laser deposition (PLD). X-ray diffraction and transmission electron microscopy characterizations revealed that the YSZ buffer layers enabled the epitaxial growth of structurally high quality ZnO films and an atomically sharp ZnO/YSZ interface, proving to be an effective epitaxial template. The epitaxial orientation relationships were revealed as follows: (0001) ZnO||(111) YSZ||(111) Si and [math2math0] ZnO||[math10] YSZ||[math10] Si. Room temperature photoluminescence spectrum of the ZnO films showed the excitonic ultraviolet emission with few green emissions relevant to oxygen vacancies in the film. Furthermore, we fabricated ZnO nanostructures on the same (111) YSZ||(111) Si substrates by simply manipulating PLD conditions for the epitaxial film growth. The size control of the ZnO nanodots was realized by varying the number of laser pulses. A blueshift behavior induced by quantum confinement was observed, as the nanodot size decreases.
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68.55.ag Semiconductors
78.40.Fy Semiconductors
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
81.15.Fg Pulsed laser ablation deposition
81.16.Mk Laser-assisted deposition
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Nonlocal spin transports in nanopillar-based lateral spin valve

S. Nonoguchi, T. Nomura, and T. Kimura

Appl. Phys. Lett. 100, 132401 (2012); http://dx.doi.org/10.1063/1.3698092 (3 pages) | Cited 1 time

Online Publication Date: 26 March 2012

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A different type lateral spin valve structure consisting of a pair of the closely located Permalloy nanopillars on a uniform copper film has been developed. From the bias-current and temperature dependences of the spin signal, the nanopillar lateral spin valve was found to have several advantages for generating the pure spin current over the conventional lateral spin valves. We also show that the limitation of the generating spin current can be enhanced by increasing the number of the spin injectors.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Origin of magnetic properties and martensitic transformation of Ni-Mn-In magnetic shape memory alloys

C. L. Tan, Y. W. Huang, X. H. Tian, J. X. Jiang, and W. Cai

Appl. Phys. Lett. 100, 132402 (2012); http://dx.doi.org/10.1063/1.3697637 (4 pages) | Cited 4 times

Online Publication Date: 26 March 2012

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The nature of unique magnetic properties and martensitic transformation of Ni2Mn1+xIn1−x shape memory alloy has been revealed by first-principles calculations. The uncommon magnetic properties occurring upon martensitic transformation are originated from the change of Mn-Mn interatomic distances. The critical value of Mn-Mn interatomic distance corresponding to the change of magnetic interactions has been determined. A decrease of the intensity of Ni 3d states at the Fermi level upon martensitic transformation has been observed for x = 0.5. Moreover, the Ni 3d-Mn 3d hybridization plays an important role in establishing the magnetic properties and driving the martensitic transformation.
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81.30.Kf Martensitic transformations
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
71.20.Be Transition metals and alloys
71.15.-m Methods of electronic structure calculations
64.70.kd Metals and alloys
75.50.Cc Other ferromagnetic metals and alloys

Magnetic and structural properties of the Fe layers in CoO/Fe/Ag(001) heterostructure

Rantej Bali, Márcio M. Soares, Aline Y. Ramos, Hélio C. N. Tolentino, Fikret Yildiz, Clemence Boudot, Olivier Proux, Maurizio De Santis, Marek Przybylski, and Jürgen Kirschner

Appl. Phys. Lett. 100, 132403 (2012); http://dx.doi.org/10.1063/1.3695158 (4 pages) | Cited 1 time

Online Publication Date: 26 March 2012

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The influence of interfacial oxidation on the magnetic behaviour of CoO covered Fe/Ag(001) is reported. Coverage with CoO causes the formation of a mixed Fe2O3-Fe3O4 interfacial oxide layer. The depth of the Fe-oxide varies with the thickness of pre-covered Fe and above 8 monolayers (MLs) of Fe the oxide depth becomes constant at 2 ML. Differences in exchange bias and coercivity obtained from magnetic field and zero field cooling nearly vanish above 8 ML Fe thickness, showing a direct correlation between the magnetic behaviour of Fe and structure of the interfacial Fe-oxide layer.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.35.Ct Interface structure and roughness
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Vv High coercivity materials
75.30.Et Exchange and superexchange interactions
75.30.Sg Magnetocaloric effect, magnetic cooling

S doping effect on the properties of double perovskite La2FeMoO6

Haiping Wu, Ruifeng Lu, Weishi Tan, Chuanyun Xiao, Kaiming Deng, and Yan Qian

Appl. Phys. Lett. 100, 132404 (2012); http://dx.doi.org/10.1063/1.3697675 (5 pages) | Cited 2 times

Online Publication Date: 26 March 2012

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The effect of S-doping on the properties of double perovskite La2FeMoO6 (LFMO) is investigated by using density-functional calculations. The results reveal that the ground state of the series La2FeMoO6−xSx is ferrimagnetic, with I4/mmm symmetry for x = 0 and 6, and I4mm symmetry for the others. With increasing the amount of S ions, the volume increases nearly linearly. The estimated Néel temperature of the compounds decreases from 537 K for La2FeMoO6 to 454 K for La2FeMoS6 upon S doping. In addition, La2FeMoO6 and the end member La2FeMoS6 both exhibit half-metallic nature, while the others behave as full metal.
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61.72.up Other materials
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Gg Ferrimagnetics
71.20.Ps Other inorganic compounds
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling

Ferromagnetic phase transition in zinc blende (Mn,Cr)S-layers grown by molecular beam epitaxy

M. Demper, W. Heimbrodt, C. Bradford, K. A. Prior, J. Kehrle, H.-A. Krug von Nidda, and A. Loidl

Appl. Phys. Lett. 100, 132405 (2012); http://dx.doi.org/10.1063/1.3697834 (3 pages)

Online Publication Date: 26 March 2012

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We studied the magnetization of zinc blende Mn1-xCrxS films embedded between diamagnetic ZnSe layers grown by molecular beam epitaxy with chromium mole fractions x ≤ 0.7. These ternary semiconductors exhibit an increasing ferromagnetic contribution with increasing x caused by competing antiferromagnetic and ferromagnetic coupling. As a result, whereas MnS in the zinc blende phase is a pure antiferromagnet, it was found that with increasing x zinc blende Mn1−xCrxS became a ferromagnet. The ferromagnetic phase transition dominates in case of x greater than about 0.5. Hence, we conclude that metastable zinc blende CrS will be a ferromagnetic material with half-metallic character in contrast to the analogous stable NiAs-structure which exhibits an antiferromagnetic phase transition.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
75.20.Ck Nonmetals

Enhanced tunnel magnetoresistance in fully epitaxial ZnO:Co-based magnetic tunnel junctions with Mg-doped ZnO barrier

Shumin He, Hongliang Bai, Guolei Liu, Qiang Li, Shishen Yan, Yanxue Chen, Liangmo Mei, Houfang Liu, Shouguo Wang, and Xiufeng Han

Appl. Phys. Lett. 100, 132406 (2012); http://dx.doi.org/10.1063/1.3698151 (3 pages) | Cited 1 time

Online Publication Date: 27 March 2012

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The fully epitaxial ZnO-based ZnO:Co/ZnO:Mg/ZnO:Co magnetic tunnel junctions were grown on Al2O3(0001) substrate by oxygen plasma-assisted molecular beam epitaxy. The magnetoresistance behavior and spin injection through ZnO:Mg barrier were investigated. An enhanced positive tunnel magnetoresistance ratio of 85.6% is observed at 1.8 T at 5 K. The junction resistance at zero magnetic field is linear with respect to temperature power law T−4/3 between 5 K and 70 K, indicating that carriers tunnel through ZnO:Mg barrier via two localized states.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.25.-b Spin polarized transport

Magnetism mechanism in ZnO and ZnO doped with nonmagnetic elements X (X = Li, Mg, and Al): A first-principles study

Q. J. Wang, J. B. Wang, X. L. Zhong, Q. H. Tan, Z. Hu, and Y. C. Zhou

Appl. Phys. Lett. 100, 132407 (2012); http://dx.doi.org/10.1063/1.3698096 (5 pages) | Cited 1 time

Online Publication Date: 28 March 2012

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First-principles calculations are performed to study the magnetism mechanism in undoped ZnO and ZnO doped with nonmagnetic elements X (X = Li, Mg, and Al). In undoped ZnO, it is found that the Zn vacancy is spin-polarized with a magnetic moment of 1.54 μB. The ferromagnetic coupling between two Zn vacancies is favorable in energy and a band coupling model is used to explain the magnetic coupling. In ZnO doped with nonmagnetic elements X, the magnetism is also attributed to the presence of Zn vacancies. The introduction of X reduces the formation energy of Zn vacancy and stabilizes it to some extent.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
61.72.jd Vacancies

Spin torque switching of 20 nm magnetic tunnel junctions with perpendicular anisotropy

M. Gajek, J. J. Nowak, J. Z. Sun, P. L. Trouilloud, E. J. O’Sullivan, D. W. Abraham, M. C. Gaidis, G. Hu, S. Brown, Y. Zhu, R. P. Robertazzi, W. J. Gallagher, and D. C. Worledge

Appl. Phys. Lett. 100, 132408 (2012); http://dx.doi.org/10.1063/1.3694270 (3 pages) | Cited 11 times

Online Publication Date: 28 March 2012

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Spin-transfer torque magnetic random access memory (STT-MRAM) is one of the most promising emerging non-volatile memory technologies. MRAM has so far been demonstrated with a unique combination of density, speed, and non-volatility in a single chip, however, without the capability to replace any single mainstream memory. In this paper, we demonstrate the basic physics of spin torque switching in 20 nm diameter magnetic tunnel junctions with perpendicular magnetic anisotropy materials. This deep scaling capability clearly indicates the STT MRAM device itself may be suitable for integration at much higher densities than previously proven.
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84.30.Sk Pulse and digital circuits

Voltage impulse induced bistable magnetization switching in multiferroic heterostructures

T. X. Nan, Z. Y. Zhou, J. Lou, M. Liu, X. Yang, Y. Gao, S. Rand, and N. X. Sun

Appl. Phys. Lett. 100, 132409 (2012); http://dx.doi.org/10.1063/1.3698363 (3 pages) | Cited 2 times

Online Publication Date: 28 March 2012

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We report on voltage impulse induced reversible bistable magnetization switching in FeGaB/lead zirconate titanate (PZT) multiferroic heterostructures at room temperature. This was realized through strain-mediated magnetoelectric coupling between ferroelectric PZT and ferromagnetic FeGaB layer. Two reversible and stable voltage-impulse induced mechanical strain states were obtained in the PZT by applying an electric field impulse with its amplitude smaller than the electric coercive field, which led to reversible voltage impulse induced bistable magnetization switching. These voltage impulse induced bistable magnetization switching in multiferroic heterostructures provides a promising approach to power efficient bistable magnetization switching that is crucial for information storage.
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75.85.+t Magnetoelectric effects, multiferroics
75.50.Bb Fe and its alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
77.80.Fm Switching phenomena

Evaluation of orbital moment in Ni-Zn ferrites: A magnetic Compton scattering study

B. L. Ahuja, H. S. Mund, Shailja Tiwari, Jagrati Sahariya, Alpa Dashora, M. Itou, and Y. Sakurai

Appl. Phys. Lett. 100, 132410 (2012); http://dx.doi.org/10.1063/1.3698385 (4 pages) | Cited 1 time

Online Publication Date: 28 March 2012

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Temperature dependent magnetic Compton profiles of Ni1−xZnxFe2O4 (x = 0.0, 0.1, 0.2) ferrites have been decomposed into component profiles to determine the site-specific magnetic moments. For a quantitative evaluation of orbital moment, the spin momentum density data have been combined with magnetization data. Interestingly, the orbital magnetic moment decreases from 0.25 ± 0.03 μB/f.u. (for x = 0.0) to 0.09 ± 0.03 μB/f.u. (for x = 0.2) which is in contrast to spin moment. A decrease in ratio of orbital to spin moments in Ni rich ferrites is explained on the basis of spin-orbit coupling and crystal field interaction.
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78.70.Ck X-ray scattering
61.80.Cb X-ray effects
61.80.Ed γ-ray effects
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
75.10.Dg Crystal-field theory and spin Hamiltonians
75.30.Cr Saturation moments and magnetic susceptibilities

Attenuation of propagating spin wave induced by layered nanostructures

K. Sekiguchi, T. N. Vader, K. Yamada, S. Fukami, N. Ishiwata, S. M. Seo, S. W. Lee, K. J. Lee, and T. Ono

Appl. Phys. Lett. 100, 132411 (2012); http://dx.doi.org/10.1063/1.3699020 (3 pages) | Cited 1 time

Online Publication Date: 30 March 2012

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Spin wave attenuation in the layered [FeNi/Pt]6/FeNi thin films was investigated by the time-domain electrical measurement. The spin-wave waveform was detected with an asymmetric coplanar strip transmission line, as an induced voltage flowing into a fast oscilloscope. We report that the amplitude of a spin-wave packet was systematically changed by controlling the thickness of a platinum layer, up to a maximum change of 50%. The virtues of spin wave, ultrafast propagation velocity and non-reciprocal emission, are preserved in this manner. This means that the Pt layer can manipulate an arbitral power-level of spin-wave input signal (reliable attenuator).
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75.30.Ds Spin waves
75.50.Bb Fe and its alloys
75.50.Tt Fine-particle systems; nanocrystalline materials
75.70.Ak Magnetic properties of monolayers and thin films
75.75.-c Magnetic properties of nanostructures
78.47.D- Time resolved spectroscopy (>1 psec)
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High-Tc superconducting quantum interference device recordings of spontaneous brain activity: Towards high-Tc magnetoencephalography

F. Öisjöen, J. F. Schneiderman, G. A. Figueras, M. L. Chukharkin, A. Kalabukhov, A. Hedström, M. Elam, and D. Winkler

Appl. Phys. Lett. 100, 132601 (2012); http://dx.doi.org/10.1063/1.3698152 (4 pages) | Cited 2 times

Online Publication Date: 27 March 2012

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We have performed single- and two-channel high transition temperature (high-Tc) superconducting quantum interference device (SQUID) magnetoencephalography (MEG) recordings of spontaneous brain activity in two healthy human subjects. We demonstrate modulation of two well-known brain rhythms: the occipital alpha rhythm and the mu rhythm found in the motor cortex. We further show that despite higher noise-levels compared to their low-Tc counterparts, high-Tc SQUIDs can be used to detect and record physiologically relevant brain rhythms with comparable signal-to-noise ratios. These results indicate the utility of high-Tc technology in MEG recordings of a broader range of brain activity.
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87.19.le EEG and MEG
87.85.D- Applied neuroscience
85.25.Dq Superconducting quantum interference devices (SQUIDs)
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The improved polarization retention through high-field charge injection in highly strained BiFeO3 thin films with preferred domain orientations

X. B. Liu, N. F. Ding, A. Q. Jiang, and P. X. Yang

Appl. Phys. Lett. 100, 132901 (2012); http://dx.doi.org/10.1063/1.3697989 (4 pages) | Cited 1 time

Online Publication Date: 26 March 2012

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We transferred nanosecond ferroelectric domain switching currents of leaky Fe-enriched bismuth ferrite thin films into polarization-electric (P-E) hysteresis loops from which nanosecond-range polarization retention as well as imprint was extracted. All the films suffer from a quick remanent polarization loss after 4 μs due to the appearance of a strong depolarization field arising from frozen compensation charges and large lattice-mismatching stresses. However, under an opposite field stressing the polarization enhances via near-electrode charge injection and approaches a theoretical value after 1000 s, which supplies an effective way to symmetrize the P-E loop of a highly strained ferroelectric thin film.
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77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
77.55.fp Other ferroelectric films

Aging associated domain evolution in the orthorhombic phase of 〈001〉 textured (K0.5Na0.5)Nb0.97Sb0.03O3 ceramics

Jianjun Yao, Jiefang Li, D. Viehland, Yunfei Chang, and Gary L. Messing

Appl. Phys. Lett. 100, 132902 (2012); http://dx.doi.org/10.1063/1.3698154 (4 pages) | Cited 2 times

Online Publication Date: 26 March 2012

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Aging effect due to domain evolution in (K0.5,Na0.5)Nb0.97Sb0.03O3 〈001〉 textured ceramics was investigated by piezoresponse force microscopy. We find that aging effect is pronounced in the orthorhombic single phase field. A more uniform and finer domain structure on the order of several hundred nanometers was observed after aging and is believed to originate from defect-migration. After poling, large domains (∼10 μm) with smooth boundaries were found in the aged condition due to the more readily redistribution of uniform and finer domain structures after aging.
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77.22.Ej Polarization and depolarization
77.65.-j Piezoelectricity and electromechanical effects
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
77.84.Ek Niobates and tantalates
61.66.Fn Inorganic compounds
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