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13 Sep 2010

Volume 97, Issue 11, Articles (11xxxx)

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Appl. Phys. Lett. 97, 113701 (2010); http://dx.doi.org/10.1063/1.3487998 (3 pages)

Sarah E. Baker, Michael D. Pocha, Allan S. P. Chang, Donald J. Sirbuly, Stefano Cabrini, Scott D. Dhuey, Tiziana C. Bond, and Sonia E. Létant
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Enhancement of magnetoresistance by hydrogen ion treatment for current-perpendicular-to-plane giant magnetoresistive films with a current-confined-path nano-oxide layer

H. Yuasa, M. Hara, S. Murakami, Y. Fuji, H. Fukuzawa, K. Zhang, M. Li, E. Schreck, P. Wang, and M. Chen

Appl. Phys. Lett. 97, 112501 (2010); http://dx.doi.org/10.1063/1.3486117 (3 pages) | Cited 3 times

Online Publication Date: 13 September 2010

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We have enhanced magnetoresistance (MR) for current-perpendicular-to-plane giant-magnetoresistive (CPP-GMR) films with a current-confined-path nano-oxide layer (CCP-NOL). In order to realize higher purity in Cu for CCPs, hydrogen ion treatment (HIT) was applied as the CuOx reduction process. By applying the HIT process, an MR ratio was increased to 27.4% even in the case of using conventional FeCo magnetic layer, from 13.0% for a reference without the HIT process. Atom probe tomography data confirmed oxygen reduction by the HIT process in the CCP-NOL. The relationship between oxygen counts and MR ratio indicates that further oxygen reduction would realize an MR ratio greater than 50%.
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75.50.Dd Nonmetallic ferromagnetic materials
81.65.-b Surface treatments
75.70.Ak Magnetic properties of monolayers and thin films
75.47.De Giant magnetoresistance

Enhanced spin signals due to native oxide formation in Ni80Fe20/Ag lateral spin valves

Goran Mihajlović, Daniel K. Schreiber, Yuzi Liu, John E. Pearson, Samuel D. Bader, Amanda K. Petford-Long, and Axel Hoffmann

Appl. Phys. Lett. 97, 112502 (2010); http://dx.doi.org/10.1063/1.3484141 (3 pages) | Cited 6 times

Online Publication Date: 13 September 2010

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Large nonlocal spin valve signals are reported in mesoscopic Ni80Fe20/Ag lateral spin valves upon exposing them to air. Magnetotransport measurements combined with transmission electron microscopy show that the formation of a native oxide layer at the Ni80Fe20/Ag interface is responsible for the large signals. The results indicate that lateral spin valves with superior performance to those based on high-resistance tunnel barriers can be achieved via controllable growth of native permalloy oxides.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
75.47.Np Metals and alloys

Size-dependent reversal of grains in perpendicular magnetic recording media measured by small-angle polarized neutron scattering

S. J. Lister, T. Thomson, J. Kohlbrecher, K. Takano, V. Venkataramana, S. J. Ray, M. P. Wismayer, M. A. de Vries, H. Do, Y. Ikeda, and S. L. Lee

Appl. Phys. Lett. 97, 112503 (2010); http://dx.doi.org/10.1063/1.3486680 (3 pages) | Cited 6 times

Online Publication Date: 13 September 2010

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Polarized small-angle neutron scattering has been used to measure the magnetic structure of a CoCrPt–SiOx thin-film data storage layer, contained within a writable perpendicular recording media, at granular (<10 nm) length scales. The magnetic contribution to the scattering is measured as the magnetization is reversed by an external field, providing unique spatial information on the switching process. A simple model of noninteracting nanomagnetic grains provides a good description of the data and an analysis of the grain-size dependent reversal provides strong evidence for an increase in magnetic anisotropy with grain diameter.
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75.50.Ss Magnetic recording materials
75.30.Gw Magnetic anisotropy
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.-d Domain effects, magnetization curves, and hysteresis
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)

Controllability of ferromagnetism in graphene

Tianxing Ma, Feiming Hu, Zhongbing Huang, and Hai-Qing Lin

Appl. Phys. Lett. 97, 112504 (2010); http://dx.doi.org/10.1063/1.3485059 (3 pages) | Cited 4 times

Online Publication Date: 13 September 2010

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We systematically study magnetic correlations in graphene within Hubbard model on a honeycomb lattice by using quantum Monte Carlo simulations. In the filling region below the Van Hove singularity, the system shows a short-range ferromagnetic correlation, which is slightly strengthened by the on-site Coulomb interaction and markedly by the next-nearest-neighbor hopping integral. The ferromagnetic properties depend on the electron filling strongly, which may be manipulated by the electric gate. Due to its resultant controllability of ferromagnetism, graphene-based samples may facilitate the development of many applications.
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75.75.-c Magnetic properties of nanostructures
75.10.Lp Band and itinerant models
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors

Enhanced magnetoresistance in lateral spin-valves

R. Adari, T. Patil, M. Murthy, R. Maheshwari, G. Vaidya, S. Ganguly, and D. Saha

Appl. Phys. Lett. 97, 112505 (2010); http://dx.doi.org/10.1063/1.3488818 (3 pages)

Online Publication Date: 14 September 2010

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The effect of feature sizes on the characteristics of lateral spintronic devices have been investigated experimentally and theoretically. It is demonstrated that confining spin-transport in the active region of a device enhances magnitude of the spin-dependent response substantially. Numerical simulation of spin-transport corroborates the experimental observations. Device characteristics are found to be a strong function of spin-polarizer and analyzer dimensions. The response is observed to attain a peak value for an optimum device feature size, and this is seen to be a function of temperature. Spin dependent effects become weaker for very small and very large devices.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.47.-m Magnetotransport phenomena; materials for magnetotransport
72.25.-b Spin polarized transport

Anisotropic magnetocaloric effect in all-ferromagnetic (La0.7Sr0.3MnO3/SrRuO3) superlattices

S. Thota, Q. Zhang, F. Guillou, U. Lüders, N. Barrier, W. Prellier, A. Wahl, and P. Padhan

Appl. Phys. Lett. 97, 112506 (2010); http://dx.doi.org/10.1063/1.3488828 (3 pages) | Cited 9 times

Online Publication Date: 14 September 2010

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We exploit the magnetic interlayer coupling in La0.7Sr0.3MnO3/SrRuO3 superlattices to realize a crossover between inverse and conventional magnetic entropy changes. Our data reveal a strong anisotropic nature of the magnetocaloric effect due to the magnetic anisotropy of the superlattice. Therefore, artificial superlattices built from ferromagnetic materials that can be used to alter the magnetic structure as well as the magnetic anisotropy, could also be utilized for tuning the magnetocaloric properties, which may open a constructive approach for magnetic refrigeration applications.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Gw Magnetic anisotropy
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)

Synthesis and magnetic properties of nanocrystals of cubic defect spinel MgMnO3

M. S. Seehra, V. Singh, S. Thota, B. Prasad, and J. Kumar

Appl. Phys. Lett. 97, 112507 (2010); http://dx.doi.org/10.1063/1.3489094 (3 pages) | Cited 4 times

Online Publication Date: 15 September 2010

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Synthesis and magnetic properties of nanocrystals (size ≃ 22 nm) of cubic spinel MgMnO3 with the defect structure [Mg2+][Mg1/32+Mn4/34+◻1/3]O4 are reported. Analysis of the magnetization M versus T (2–370 K) and M versus H (up to 65 kOe) data shows a blocking temperature TB ≃ 11 K and an estimated Néel temperature TN ∼ 150 K above which the Weiss temperature θ = −7 K and μ = 3.91 μB/Mn4+. For TB<T<TN, fit of the M versus H data to modified Langevin function yields 35 μB as magnetic moment/particle, resulting from the defect structure.
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75.75.Cd Fabrication of magnetic nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
61.72.-y Defects and impurities in crystals; microstructure
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.07.Bc Nanocrystalline materials

Influence of slanted nanostripe edges on the dynamics of magnetic domain walls

S. Glathe, M. Zeisberger, R. Mattheis, and D. Hesse

Appl. Phys. Lett. 97, 112508 (2010); http://dx.doi.org/10.1063/1.3489359 (3 pages) | Cited 3 times

Online Publication Date: 15 September 2010

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We report a combined experimental and theoretical study on the influence of slanted nanostripe edges on the magnetic domain wall (DW) dynamics in permalloy nanostripes. The DWs show a significantly different behavior in the same sample depending on the magnetization configuration in the DW. We explain these characteristics via a difference of the stray field generated by the out-of-plane magnetization inside the DW in the nanostripe edge region during DW motion.
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75.75.-c Magnetic properties of nanostructures
75.60.Ch Domain walls and domain structure
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Bb Fe and its alloys

Epitaxial EuO thin films on GaAs

A. G. Swartz, J. Ciraldo, J. J. I. Wong, Yan Li, Wei Han, Tao Lin, S. Mack, J. Shi, D. D. Awschalom, and R. K. Kawakami

Appl. Phys. Lett. 97, 112509 (2010); http://dx.doi.org/10.1063/1.3490649 (3 pages) | Cited 10 times

Online Publication Date: 17 September 2010

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We demonstrate the epitaxial growth of EuO on GaAs by reactive molecular beam epitaxy. Thin films are grown in an adsorption-controlled regime with the aid of an MgO diffusion barrier. Despite the large lattice mismatch, it is shown that EuO grows well on MgO(001) with excellent magnetic properties. Epitaxy on GaAs is cube-on-cube and longitudinal magneto-optic Kerr effect measurements demonstrate a large Kerr rotation of 0.57°, a significant remanent magnetization, and a Curie temperature of 69 K.
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68.55.A- Nucleation and growth
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.20.Ls Magneto-optical effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Demonstration of single-flux-quantum readout operation for superconducting single-photon detectors

Hirotaka Terai, Shigehito Miki, Taro Yamashita, Kazumasa Makise, and Zhen Wang

Appl. Phys. Lett. 97, 112510 (2010); http://dx.doi.org/10.1063/1.3484965 (3 pages) | Cited 4 times

Online Publication Date: 17 September 2010

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A readout circuit using superconducting single-flux-quantum (SFQ) circuits has been developed to realize an independently addressable array of superconducting single-photon detectors (SSPDs). We tested the SFQ readout circuits by connecting with SSPDs. The error rates of readout circuits were below 10−5 for input signal amplitude of greater than 18.2 μA. Detection efficiencies (DEs) for single-photon incidents were measured both with and without the connection of a readout circuit. The observed DEs traced almost the same curves regardless of the connection of the readout circuit, except that the SSPD is likely to latch by connecting the readout circuit.
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85.25.Oj Superconducting optical, X-ray, and γ-ray detectors (SIS, NIS, transition edge)
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