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18 Feb 2013

Volume 102, Issue 7, Articles (07xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 102, 073101 (2013); http://dx.doi.org/10.1063/1.4790646 (4 pages)

V. Reboud, J. Romero-Vivas, P. Lovera, N. Kehagias, T. Kehoe, G. Redmond, and C. M. Sotomayor Torres
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Origin of the defects-induced ferromagnetism in un-doped ZnO single crystals

Peng Zhan, Zheng Xie, Zhengcao Li, Weipeng Wang, Zhengjun Zhang, Zhuoxin Li, Guodong Cheng, Peng Zhang, Baoyi Wang, and Xingzhong Cao

Appl. Phys. Lett. 102, 071914 (2013); http://dx.doi.org/10.1063/1.4793574 (5 pages)

Online Publication Date: 22 February 2013

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We clarified, in this Letter, that in un-doped ZnO single crystals after thermal annealing in flowing argon, the defects-induced room-temperature ferromagnetism was originated from the surface defects and specifically, from singly occupied oxygen vacancies denoted as F+, by the optical and electrical properties measurements as well as positron annihilation analysis. In addition, a positive linear relationship was observed between the ferromagnetism and the F+ concentration, which is in support with the above clarification.
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61.72.jd Vacancies
72.80.Ey III-V and II-VI semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
78.40.Fy Semiconductors
81.05.Dz II-VI semiconductors
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Observation of the electron-accumulation layer at the surface of InN by cross-sectional micro-Raman spectroscopy

YongJin Cho, Manfred Ramsteiner, and Oliver Brandt

Appl. Phys. Lett. 102, 072101 (2013); http://dx.doi.org/10.1063/1.4792837 (4 pages)

Online Publication Date: 19 February 2013

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We study plasmon-related excitations in InN by micro-Raman spectroscopy. The surface sensitivity of Raman scattering is found to be strongly enhanced for backscattering from cleaved edges of thick films. This fact enables us to observe the electron accumulation layer at the surface of InN and to deduce the associated volume charge density.
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73.20.At Surface states, band structure, electron density of states
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.30.Hv Other nonmetallic inorganics
68.55.ag Semiconductors

Space charge polarization induced memory in SmNiO3/Si transistors

Sang Hyeon Lee, Moonkyung Kim, Sieu D. Ha, Jo-Won Lee, Shriram Ramanathan, and Sandip Tiwari

Appl. Phys. Lett. 102, 072102 (2013); http://dx.doi.org/10.1063/1.4790394 (4 pages)

Online Publication Date: 19 February 2013

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The correlated oxide, SmNiO3 (SNO), is characterized and explored as a phase transition material in silicon capacitors and transistors with SNO as a floating gate sandwiched between silicon dioxide gate insulators. The structures show hysteresis at low bias voltages. The capacitance and its voltage hysteresis window increase as the frequency of the applied field decreases with a response time of polarization of above a microsecond. This suggests a space charge polarization dominated by low frequency permittivity response. Instability of 3+ oxidation state of Ni and presence of oxygen vacancies are believed to lead to a polarization effect through Poole-Frenkel charge trapping/de-trapping. Metal-oxide-semiconductor transistors show counterclockwise voltage hysteresis consistent with polarization switching effect. The stored information decays gradually due to the depolarization field with retention times of the order of 10 s at room temperature.
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85.30.Tv Field effect devices
84.30.Sk Pulse and digital circuits
84.32.Tt Capacitors

Temperature sensitive photoconductivity observed in InN layers

Lei Guo, Xinqiang Wang, Li Feng, Xiantong Zheng, Guang Chen, Xuelin Yang, Fujun Xu, Ning Tang, Liwu Lu, Weikun Ge, and Bo Shen

Appl. Phys. Lett. 102, 072103 (2013); http://dx.doi.org/10.1063/1.4793190 (5 pages)

Online Publication Date: 19 February 2013

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Photoconductivity has been systematically studied in unintentionally doped n-type InN film with super-bandgap excitation (1.53 eV) at temperatures varying in the range of 100–300 K. A negative photoconductivity is observed at room temperature, whereas it gradually changes to be positive with decreasing temperature. Transition temperature from negative to positive photoconductivity is found to be greatly related to the residual electron concentration as the higher the electron concentration, the lower the transition temperature. An energy band model including a donor state with large lattice relaxation as well as a recombination center is proposed, which explains the experimental observation well.
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73.50.Pz Photoconduction and photovoltaic effects
73.61.Ey III-V semiconductors
71.55.Eq III-V semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance

Synchrotron radiation based cross-sectional scanning photoelectron microscopy and spectroscopy of n-ZnO:Al/p-GaN:Mg heterojunction

Kai-Hsuan Lee, Ping-Chuan Chang, Tse-Pu Chen, Sheng-Po Chang, Hung-Wei Shiu, Lo-Yueh Chang, Chia-Hao Chen, and Shoou-Jinn Chang

Appl. Phys. Lett. 102, 072104 (2013); http://dx.doi.org/10.1063/1.4793434 (5 pages)

Online Publication Date: 22 February 2013

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Al-doped ZnO (AZO) deposited by radio frequency co-sputtering is formed on epitaxial Mg-doped GaN template at room temperature to achieve n-AZO/p-GaN heterojunction. Alignment of AZO and GaN bands is investigated using synchrotron radiation based cross-sectional scanning photoelectron microscopy and spectroscopy on the nonpolar side-facet of a vertically c-axis aligned heterostructure. It shows type-II band configuration with valence band offset of 1.63 ± 0.1 eV and conduction band offset of 1.61 ± 0.1 eV, respectively. Rectification behavior is clearly observed, with a ratio of forward-to-reverse current up to six orders of magnitude when the bias is applied across the p-n junction.
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81.05.Dz II-VI semiconductors
81.05.Ea III-V semiconductors
81.15.Cd Deposition by sputtering
71.20.Nr Semiconductor compounds
73.40.Ei Rectification
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Interface charge engineering at atomic layer deposited dielectric/III-nitride interfaces

Ting-Hsiang Hung, Sriram Krishnamoorthy, Michele Esposto, Digbijoy Neelim Nath, Pil Sung Park, and Siddharth Rajan

Appl. Phys. Lett. 102, 072105 (2013); http://dx.doi.org/10.1063/1.4793483 (4 pages)

Online Publication Date: 22 February 2013

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Interface charges at atomic layer deposited Al2O3/III-nitride interfaces were investigated for III-nitride layers of different polarity. A large positive sheet charge density is induced at the Al2O3/III-nitride interface on all the orientations of GaN and Ga-polar AlGaN, and this sheet charge can be significantly altered using post-metallization anneals. It is proposed that the charges are caused by interfacial defects that can be passivated and neutralized through a H2 based anneal. Tailoring of the interface charge density described here can be used to improve critical device characteristics such as gate leakage and electron transport, and for lateral electrostatic engineering.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.Rv Passivation
61.72.Cc Kinetics of defect formation and annealing
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Intrinsic electronic switching time in ultrathin epitaxial vanadium dioxide thin film

Ayan Kar, Nikhil Shukla, Eugene Freeman, Hanjong Paik, Huichu Liu, Roman Engel-Herbert, S. S. N. Bhardwaja, Darrell G. Schlom, and Suman Datta

Appl. Phys. Lett. 102, 072106 (2013); http://dx.doi.org/10.1063/1.4793537 (5 pages)

Online Publication Date: 22 February 2013

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This letter investigates the intrinsic electronic switching time associated with the insulator-to-metal phase transition in epitaxial single crystal vanadium dioxide (VO2) thin films using impedance spectroscopy and ac conductivity measurements. The existence of insulating and metallic phase coexistence, intrinsic to the epitaxial (001) oriented VO2 thin film grown on a (001) rutile TiO2 substrate, results in a finite capacitance being associated with the VO2 films in their insulating phase that limits the electronic switching speed. Insights into the switching characteristics and their correlation to the transport mechanism in the light of phase coexistence are obtained by performing a detailed scaling study on VO2 two-terminal devices.
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72.60.+g Mixed conductivity and conductivity transitions
73.61.Ng Insulators
71.30.+h Metal-insulator transitions and other electronic transitions
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Enhanced inverse spin-Hall effect in ultrathin ferromagnetic/normal metal bilayers

T. D. Skinner, H. Kurebayashi, D. Fang, D. Heiss, A. C. Irvine, A. T. Hindmarch, M. Wang, A. W. Rushforth, and A. J. Ferguson

Appl. Phys. Lett. 102, 072401 (2013); http://dx.doi.org/10.1063/1.4792693 (4 pages)

Online Publication Date: 19 February 2013

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Electrically detected ferromagnetic resonance is measured in microdevices patterned from ultra-thin Co/Pt bilayers. Spin pumping and rectification voltages are observed and distinguished via their angular dependence. The spin-pumping voltage shows an unexpected increase as the cobalt thickness is reduced below 2 nm. This enhancement allows more efficient conversion of spin to charge current.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.25.-b Spin polarized transport
72.20.My Galvanomagnetic and other magnetotransport effects
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance

Enhancement of the metal-insulator transition temperature in La0.7Ca0.3MnO3 film by magnetic nanodots

Rong-Rong Ma, Xian-Peng Zhang, Feng-Xian Jiang, Zhi-Yong Quan, G. A. Gehring, and Xiao-Hong Xu

Appl. Phys. Lett. 102, 072402 (2013); http://dx.doi.org/10.1063/1.4792762 (4 pages)

Online Publication Date: 19 February 2013

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The magnetic and transport properties of a single layer of La0.7Ca0.3MnO3 are compared with one topped with magnetic nanodots formed from oxides of iron. Remarkably enhanced magnetization and metal-insulator transition temperature were observed for the decorated film capped with In2O3. The saturation magnetization increased by ∼35%, and the metal-insulator transition temperature increased from 75 K to 145 K at zero field. However, no enhancement was observed for either the La0.7Ca0.3MnO3 film with uncapped magnetic dots or the bilayer formed from La0.7Ca0.3MnO3 and In2O3.
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72.60.+g Mixed conductivity and conductivity transitions
73.61.Ng Insulators
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films

Micromagnetic modeling of experimental hysteresis loops for heterogeneous electrodeposited cobalt films

Matthew P. Seymour, Ian Wilding, Ben Xu, Jason I. Mercer, Martin L. Plumer, Kristin M. Poduska, Anand Yethiraj, and Johan van Lierop

Appl. Phys. Lett. 102, 072403 (2013); http://dx.doi.org/10.1063/1.4793209 (4 pages) | Cited 1 time

Online Publication Date: 20 February 2013

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Micromagnetic modeling provides a realistic description of the magnetic switching behavior in electrodeposited Co thin films that are either uniform (untemplated) or templated with an array of sub-micron spheres. Quantitative agreement between experimental results and simulations based on the Landau-Lifshitz-Gilbert equations is achieved for both in-plane and perpendicular MH loops at two temperatures. By accounting for the sweep-rate dependence in coercivity values from simulated loops (with sweep rates 104–10−1 Oe/ns) and then extrapolating to the experimental regime (measurement times of 10–100 s), a self-consistent set of microscopic parameters is established to accommodate the complexity of the electrodeposited films.
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75.70.Ak Magnetic properties of monolayers and thin films
81.15.Pq Electrodeposition, electroplating
82.45.Qr Electrodeposition and electrodissolution
68.55.jd Thickness
75.78.Jp Ultrafast magnetization dynamics and switching
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Observation of circular dichroism in (001)-oriented P-I-N InGaAs/GaAs quantum wells without magnetic field

J. L. Yu, Y. H. Chen, Y. Liu, C. Y. Jiang, H. Ma, L. P. Zhu, and X. D. Qin

Appl. Phys. Lett. 102, 072404 (2013); http://dx.doi.org/10.1063/1.4793211 (5 pages)

Online Publication Date: 20 February 2013

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The (001)-oriented P-I-N InGaAs/GaAs quantum wells (QWs) are studied by means of helicity dependent spin photocurrent. We have observed an unexpected circular dichroism effect along [001] direction in the QWs without an applied magnetic field. The circular polarization rate can be linearly tuned by the applied DC current flowing along [001] direction, and its value is enhanced more than one order in an InGaAs/GaAs vertical-cavity surface-emitting laser with distributed Bragg reflectors than that in a common InGaAs/GaAs QWs. This experiment indicates a type of spin-splitting in (001)-grown P-I-N InGaAs/GaAs quantum wells induced by space inversion asymmetry introduced by residual strain which is previously overlooked.
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81.05.Ea III-V semiconductors
81.07.St Quantum wells
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.55.Px Semiconductor lasers; laser diodes
73.63.Hs Quantum wells
78.67.De Quantum wells

Real-time observation of electrical vortex core switching

Kunihiro Nakano, Kenji Tanabe, Ryo Hiramatsu, Daichi Chiba, Norikazu Ohshima, Shinya Kasai, Tomonori Sato, Yoshinobu Nakatani, Koji Sekiguchi, Kensuke Kobayashi, and Teruo Ono

Appl. Phys. Lett. 102, 072405 (2013); http://dx.doi.org/10.1063/1.4793212 (3 pages) | Cited 1 time

Online Publication Date: 20 February 2013

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A single vortex-core switching induced by current injection into a ferromagnetic disk is detected in real time using a three-terminal device with the tunneling magnetoresistance junction. The real time observation reveals that the electrical core switching is completed within a few 100 ps. It is also found that the core switching takes place at the specific positions inside the disk.
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75.47.-m Magnetotransport phenomena; materials for magnetotransport
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Origin of room temperature ferromagnetism in MgO films

Jing Li, Yinzhu Jiang, Yong Li, Deren Yang, Yongbing Xu, and Mi Yan

Appl. Phys. Lett. 102, 072406 (2013); http://dx.doi.org/10.1063/1.4793308 (4 pages) | Cited 1 time

Online Publication Date: 21 February 2013

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We report a systematic study of the crystallinity dependence of room-temperature ferromagnetism (RTFM) in pure MgO thin films prepared by pulsed laser deposition. A sequential transition from ferromagnetism to diamagnetism as a function of deposition temperature is observed. All the samples deposited from room temperature (RT) to 200 °C show clear RTFM, and the magnetization decreases monotonically with the increase of the substrate temperature, whereas the MgO film grown at 300 °C shows diamagnetism behavior like bulk MgO sample. The maximum saturation magnetization of 8 emu/cm3 is obtained for the MgO film deposited at RT, which degrades dramatically after crystallization under the annealing in both vacuum and air atmosphere. Further photoluminescence and X-ray photoelectron spectroscopies reveal that the ferromagnetism in the MgO thin films is correlated directly with the Mg vacancies.
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75.70.Ak Magnetic properties of monolayers and thin films
75.20.Ck Nonmetals
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Nt Magnetic annealing and temperature-hysteresis effects

Evidence of martensitic phase transitions in magnetic Ni-Mn-In thin films

A. Sokolov, Le Zhang, I. Dubenko, T. Samanta, S. Stadler, and N. Ali

Appl. Phys. Lett. 102, 072407 (2013); http://dx.doi.org/10.1063/1.4793421 (3 pages)

Online Publication Date: 21 February 2013

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Ni50Mn35In15 Heusler alloy thin films (with thicknesses of about 10 nm) have been grown on single crystal MgO and SrTiO3 (STO) (100) substrates using a laser-assisted molecular beam epitaxy method. Films of mixed austenitic and martensitic phases and of pure martensitic phase have been detected for those grown on MgO and STO substrates, respectively. Thermomagnetic curves were measured using a SQUID magnetometer and are consistent with those of off-stoichiometric In-based bulk Heusler alloys, including a martensitic transition at T = 315 K for films grown on MgO. The differences in the properties of the films grown on MgO and STO are discussed.
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81.30.Kf Martensitic transformations
64.70.kd Metals and alloys
72.15.Jf Thermoelectric and thermomagnetic effects
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Defect-induced ferromagnetism in ZnO nanoparticles prepared by mechanical milling

The-Long Phan, Y. D. Zhang, D. S. Yang, N. X. Nghia, T. D. Thanh, and S. C. Yu

Appl. Phys. Lett. 102, 072408 (2013); http://dx.doi.org/10.1063/1.4793428 (5 pages)

Online Publication Date: 21 February 2013

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Though ZnO is known as a diamagnetic material, recent studies have revealed that its nanostructures can be ferromagnetic (FM). The FM origin has been ascribed to intrinsic defects. This work shines light on an alternate method based on mechanical milling to induce defect-related ferromagnetism in ZnO nanoparticles (NPs) from initial diamagnetic ZnO powders. Our idea is motivated by the fact that mechanical milling introduces more defects to a ground material. We point out that the FM order increases with increasing the density of defects in ZnO NPs. The experimental results obtained from analyzing X-ray absorption, electron spin resonance, and Raman scattering spectra demonstrate that the ferromagnetism in ZnO NPs is due to intrinsic defects mainly related to oxygen and zinc vacancies. Among these, zinc vacancies play a decisive role in introducing a high FM order in ZnO NPs.
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75.75.Cd Fabrication of magnetic nanostructures
75.20.Ck Nonmetals
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
75.50.Tt Fine-particle systems; nanocrystalline materials
78.70.Dm X-ray absorption spectra

Enhanced texture in die-upset nanocomposite magnets by Nd-Cu grain boundary diffusion

Xin Tang (唐鑫), Renjie Chen (陈仁杰), Wenzong Yin (尹文宗), Jinzhi Wang (汪金芝), Xu Tang (唐旭), Don Lee (李 东), and Aru Yan (闫阿儒)

Appl. Phys. Lett. 102, 072409 (2013); http://dx.doi.org/10.1063/1.4793429 (5 pages)

Online Publication Date: 21 February 2013

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Bulk anisotropic nanocomposite Nd2Fe14B/α-Fe magnets were prepared by hot pressing and die upsetting coupled with Nd-Cu grain boundary diffusion. The hot workability of nanocomposite magnets is enhanced dramatically by grain boundary diffusion of low melt point Nd-Cu alloy, resulting in a strong anisotropy by die upsetting. The microstructure of die-upset nanocomposite magnets is identical with that of the traditional die-upset rare earth-rich magnets. The coercivity, remanence, and squareness degree of demagnetization curves are optimized. The observation for microstructures and the analysis of magnetic properties suggest that the grain boundary diffusion mainly occurs in the hot deformation process.
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81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
75.75.Cd Fabrication of magnetic nanostructures
61.72.Mm Grain and twin boundaries
66.30.Pa Diffusion in nanoscale solids
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Spin polarized current through Cu-DNA modulated by a gate voltage

D. W. Kang, X. P. Hao, X. Z. Li, L. B. Li, and S. J. Xie

Appl. Phys. Lett. 102, 072410 (2013); http://dx.doi.org/10.1063/1.4793479 (4 pages)

Online Publication Date: 21 February 2013

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Spin polarized current through DNA molecule doped with one Cu2+ ion is studied. It is found that the spin polarization is sensitive to the position of the Cu2+ ion doping. In order to obtain a steady and large spin polarization, the metal ion should be doped at the end of the DNA molecule. We propose the possibility of controlling the spin polarization using a gate voltage. This control is originated from electron precession, which is induced by Rashba spin-orbit coupling.
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85.65.+h Molecular electronic devices
87.14.gk DNA
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
72.25.-b Spin polarized transport

Strain induced giant magnetism in epitaxial Fe16N2 thin film

Nian Ji, Valeria Lauter, Xiaowei Zhang, Hailemariam Ambaye, and Jian-Ping Wang

Appl. Phys. Lett. 102, 072411 (2013); http://dx.doi.org/10.1063/1.4792706 (4 pages)

Online Publication Date: 21 February 2013

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We report a direct observation of giant saturation magnetization in Fe16N2. By exploiting thin film epitaxy, which provides controlled biaxial stress to create lattice distortion, we demonstrate that giant magnetism can be established in Fe16N2 thin film coherently grown on MgO (001) substrate. Explored by polarized neutron reflectometry, the depth-dependent saturation magnetic induction (Bs) of epitaxial Fe16N2 thin films is visualized, which reveals a strong correlation with the in-plane lattice parameter and tensile strain developed at near substrate interface. With controlled growth process and dimension adjustment, the Bs of these films can be modulated over a broad range, from ∼2.1 Tesla (T) (normal Bs) up to ∼3.1 T (giant Bs).
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75.70.Ak Magnetic properties of monolayers and thin films
62.20.F- Deformation and plasticity
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.-i Magnetic properties of thin films, surfaces, and interfaces

Concurrent improvement of magneto-optical and perpendicular magnetic properties in CoPt/Ag stacked structures with ZnO intermediate thin layers

H. Yamane

Appl. Phys. Lett. 102, 072412 (2013); http://dx.doi.org/10.1063/1.4793232 (4 pages)

Online Publication Date: 22 February 2013

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The magneto-optical properties of stacked-layer structures consisting of hcp-Co80Pt20 thin films and noble metal underlayers were investigated under polar Kerr measurement conditions. For CoPt/Ag stacked films, insertion of a 2-nm-thick ZnO layer into the interface resulted in the concurrent improvement of the magneto-optical enhancement at the plasma edge of Ag and perpendicular magnetic anisotropy. An ideal square out-of-plane hysteresis loop with a large Kerr rotation of approximately 1.25° was obtained in the CoPt/ZnO/Ag stacked structure. Moreover, heat treatment in a vacuum resulted in further improvement of the perpendicular magneto-optical properties in the stacked structures with thin CoPt layers.
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78.20.Ls Magneto-optical effects
81.40.Gh Other heat and thermomechanical treatments
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Observation of the spin Seebeck effect in epitaxial Fe3O4 thin films

R. Ramos, T. Kikkawa, K. Uchida, H. Adachi, I. Lucas, M. H. Aguirre, P. Algarabel, L. Morellón, S. Maekawa, E. Saitoh, and M. R. Ibarra

Appl. Phys. Lett. 102, 072413 (2013); http://dx.doi.org/10.1063/1.4793486 (5 pages) | Cited 1 time

Online Publication Date: 22 February 2013

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We report the experimental observation of the spin Seebeck effect in magnetite thin films. The signal observed at temperatures above the Verwey transition is a contribution from both the anomalous Nernst (ANE) and spin Seebeck (SSE) effects. The contribution from the ANE of the Fe3O4 layer to the SSE is found to be negligible due to the resistivity difference between Fe3O4 and Pt layers. Below the Verwey transition, the SSE is free from the ANE of the ferromagnetic layer and it is also found to dominate over the ANE due to magnetic proximity effect on the Pt layer.
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72.20.Pa Thermoelectric and thermomagnetic effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.47.Lx Magnetic oxides
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
72.20.My Galvanomagnetic and other magnetotransport effects
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Radiation-suppressed superconducting quantum bit in a planar geometry

Martin Sandberg, Michael R. Vissers, Thomas A. Ohki, Jiansong Gao, José Aumentado, Martin Weides, and David P. Pappas

Appl. Phys. Lett. 102, 072601 (2013); http://dx.doi.org/10.1063/1.4792698 (4 pages)

Online Publication Date: 19 February 2013

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We present a superconducting transmon qubit circuit design based on large, coplanar capacitor plates and a microstrip resonator. The microstrip geometry, with the ground plane on the back, enhances access to the circuit for state preparation and measurement relative to other designs. The device is fabricated on a silicon substrate using low loss, stoichiometric titanium nitride for the capacitor plates and a single small aluminium/aluminium-oxide/aluminium junction. We observe relaxation and coherence times of 11.7 ± 0.2 μs and 9.6 ± 0.5 μs, respectively, using spin echo. Calculations show that the close proximity of the superconducting back-plane has the added advantage of suppressing the otherwise high radiation loss of the qubit.
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85.25.Am Superconducting device characterization, design, and modeling
74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
74.55.+v Tunneling phenomena: single particle tunneling and STM
61.66.Bi Elemental solids
61.66.Dk Alloys

Current-controllable planar S-(S/F)-S Josephson junction

O. Vávra, W. Pfaff, R. Monaco, M. Aprili, and C. Strunk

Appl. Phys. Lett. 102, 072602 (2013); http://dx.doi.org/10.1063/1.4792213 (3 pages)

Online Publication Date: 20 February 2013

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We report on the experimental realization of a current-controllable lateral S-(S/F)-S Josephson junction based on the inverse proximity effect in the superconductor-ferromagnet bilayer (S/F). The dependence of the critical current on the magnetic field Ic(B) shows a Fresenel-like pattern, which could qualitatively be understood with the theory of Josephson junctions in a magnetic field gradient. The amplitude and the period of the Ic(B) pattern can be controlled by spin-polarized quasiparticles injection into the weak link. The period change suggests controllability of effective area of the Josephson junction. Furthermore, a temperature-induced transition from a weak-link behavior to a strong coupling between the superconducting banks is also observed in these lateral Josephson junctions.
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74.50.+r Tunneling phenomena; Josephson effects
74.25.Sv Critical currents
74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions

Penetration depth of MgB2 measured using Josephson junctions and SQUIDs

Daniel Cunnane, Chenggang Zhuang, Ke Chen, X. X. Xi, Jie Yong, and T. R. Lemberger

Appl. Phys. Lett. 102, 072603 (2013); http://dx.doi.org/10.1063/1.4793194 (4 pages) | Cited 1 time

Online Publication Date: 21 February 2013

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The penetration depth of MgB2 was measured using two methods of different mechanisms. The first method used MgB2 Josephson junctions and the magnetic field dependence of the junction critical current. The second method deduced the penetration depth from the inductance of a MgB2 microstrip used to modulate the voltage of a MgB2 DC SQUID. The two methods showed a consistent value of the low-temperature penetration depth for MgB2 to be about 40 nm. Both the small penetration depth value and its temperature dependence are in agreement with a microscopic theory for MgB2 in the clean limit.
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74.50.+r Tunneling phenomena; Josephson effects
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Sv Critical currents
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Temperature dependent polarization switching properties of ferroelectric Pb0.92La0.08Zr0.52Ti0.48Oδ films grown on nickel foils

Beihai Ma, Zhongqiang Hu, Shanshan Liu, Manoj Narayanan, and U. (Balu) Balachandran

Appl. Phys. Lett. 102, 072901 (2013); http://dx.doi.org/10.1063/1.4793304 (4 pages) | Cited 2 times

Online Publication Date: 19 February 2013

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Ferroelectric Pb0.92La0.08Zr0.52Ti0.48Oδ films (≈2-μm thickness) were grown on LaNiO3-buffered nickel foils by chemical solution deposition. Their ferroelectric and dielectric properties were measured as a function of temperature. With increasing temperature from room temperature to 200 °C, back-switching polarization increased while spontaneous polarization, remanent polarization, and coercive field decreased. The domain wall energy barrier was determined from the temperature-dependent back-switching polarization. Decreased irreversible/extrinsic and reversible/intrinsic dielectric responses were observed with increasing frequency. The ratio of irreversible to reversible contributions to dielectric nonlinearity was analyzed by the Rayleigh law. This ratio decreased with increasing frequency from 500 Hz to 500 kHz.
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77.80.Fm Switching phenomena
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.at Other materials
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis

Observation of large magnetodielectric and direct magnetoelectric behavior in LCMO/PVDF 0-3 nanocomposites

Debabrata Bhadra, Md. G. Masud, S. K. De, and B. K. Chaudhuri

Appl. Phys. Lett. 102, 072902 (2013); http://dx.doi.org/10.1063/1.4793307 (5 pages)

Online Publication Date: 20 February 2013

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A two-phase multifunctional La2CoMnO6 (LCMO)/Poly-vinylidene fluoride 0–3 flexible nanocomposite (NCOMP) thick films have been prepared. Interestingly, this NCOMP shows linear increase of magnetoelectric voltage coefficient (MVC) with applied dc magnetic-bias fields up to 5 kOe, exhibiting no sign of hysteresis. For the typical LCMO concentration, fLCMO = 0.15, the maximum MVC measured is 1.45 mV cm−1 Oe−1 (using 50 kHz resonant signal). This low dielectric loss (∼0.12) NCOMP also showed intriguing high magnetodielectric effect (∼10%) around the ferromagnetic transition temperature (Tc ∼ 230 K) with minimal leakage current. Such results make the present nanocomposite significantly important for the development of magnetic field tuned electronic devices.
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75.85.+t Magnetoelectric effects, multiferroics
75.75.Cd Fabrication of magnetic nanostructures
77.55.Nv Multiferroic/magnetoelectric films
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Ak Magnetic properties of monolayers and thin films
77.22.Gm Dielectric loss and relaxation
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