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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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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)

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
FREE

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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