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10 May 2010

Volume 96, Issue 19, Articles (19xxxx)

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Appl. Phys. Lett. 96, 193101 (2010); http://dx.doi.org/10.1063/1.3425776 (3 pages)

J. J. Zhang, N. Hrauda, H. Groiss, A. Rastelli, J. Stangl, F. Schäffler, O. G. Schmidt, and G. Bauer
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Vortex manipulation in a superconducting matrix with view on applications

M. V. Milošević and F. M. Peeters

Appl. Phys. Lett. 96, 192501 (2010); http://dx.doi.org/10.1063/1.3425672 (3 pages) | Cited 2 times

Online Publication Date: 10 May 2010

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We show how a single flux quantum can be effectively manipulated in a superconducting film with a matrix of blind holes. Such a sample can serve as a basic memory element, where the position of the vortex in a k×l matrix of pinning sites defines the desired combination of n bits of information (2n = k×l). Vortex placement is achieved by strategically applied current and the resulting position is read out via generated voltage between metallic contacts on the sample. Such a device can also act as a controllable source of a nanoengineered local magnetic field for, e.g., spintronics applications.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Wx Vortex pinning (includes mechanisms and flux creep)
85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits

Flexural deformation in a compositionally stepped ferrite and magnetoelectric effects in a composite with piezoelectrics

S. K. Mandal, G. Sreenivasulu, V. M. Petrov, and G. Srinivasan

Appl. Phys. Lett. 96, 192502 (2010); http://dx.doi.org/10.1063/1.3428774 (3 pages) | Cited 13 times

Online Publication Date: 10 May 2010

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The nature of strain mediated magnetoelectric (ME) coupling is investigated in laminates of lead zirconate titanate (PZT) and compositionally stepped ferrite with grading of piezomagnetic coefficient. ME effects that could only be attributed to grading related bending strain are observed in a trilayer of ferrite and oppositely poled PZT. It is shown that in a bilayer, grading induced flexural strain counteracts bending moment due to structural asymmetry and enhances ME coupling by a factor of 2. A zero-bias field ME effect is observed in such laminates. The graded composites are of interest for self-biased magnetic field sensors.
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81.40.Lm Deformation, plasticity, and creep
75.85.+t Magnetoelectric effects, multiferroics
75.50.Gg Ferrimagnetics
75.80.+q Magnetomechanical effects, magnetostriction
77.84.Cg PZT ceramics and other titanates
77.65.Ly Strain-induced piezoelectric fields

The effect of trapping superparamagnetic beads on domain wall motion

Matthew T. Bryan, Julian Dean, Thomas Schrefl, Faye E. Thompson, John Haycock, and Dan A. Allwood

Appl. Phys. Lett. 96, 192503 (2010); http://dx.doi.org/10.1063/1.3428775 (3 pages) | Cited 9 times

Online Publication Date: 10 May 2010

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Domain walls may act as localized field sources to trap and move superparamagnetic beads for manipulating biological cells and DNA. The interaction between beads of various diameters and a wall is investigated using a combination of micromagnetic and analytical models. Domain walls can transport beads under applied magnetic fields but the mutual attraction between the bead and wall causes drag forces affecting the bead to couple into the wall motion. Therefore, the interaction with the bead causes a fundamental change in the domain wall dynamics, reducing the wall mobility by five orders of magnitude.
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87.17.-d Cell processes
87.16.-b Subcellular structure and processes
87.14.gk DNA

Electric-field-control of magnetic remanence of NiFe2O4 thin film epitaxially grown on Pb(Mg1/3Nb2/3)O3–PbTiO3

Jung Hwan Park, Young Kyu Jeong, Sangwoo Ryu, Jong Yeog Son, and Hyun Myung Jang

Appl. Phys. Lett. 96, 192504 (2010); http://dx.doi.org/10.1063/1.3427311 (3 pages) | Cited 5 times

Online Publication Date: 11 May 2010

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We propose an asymmetric bilayer structure in which the magnetic remanence (MR) is controlled by the in-plane strain of the top NiFe2O4 (NFO) layer epitaxially constrained by the bottom Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) substrate. In this asymmetric structure, an electric-field-induced giant piezoelectric strain from the bottom PMN-PT layer is effectively transferred to the top NFO layer. We have shown that the room-temperature magnetic remanence (MR) of the 100-nm-thick NFO layer is enhanced by 46% when an electric-field-induced in-plane compressive strain is about −0.1%. Synchrotron x-ray absorption near edge structure study supports a scenario of the cation-charge redistribution between Ni2+ and Fe3+ ions under the condition of an electric-field-induced in-plane compressive strain.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.60.Bs Mechanical and acoustical properties
75.80.+q Magnetomechanical effects, magnetostriction
77.65.Ly Strain-induced piezoelectric fields
78.70.Dm X-ray absorption spectra
75.70.Ak Magnetic properties of monolayers and thin films

Neutron scattering measurements of magnetic excitations in Gd/Y superlattices

A. T. D. Grünwald, A. R. Wildes, W. Schmidt, E. V. Tartakovskaya, G. Nowak, K. Theis-Bröhl, and A. Schreyer

Appl. Phys. Lett. 96, 192505 (2010); http://dx.doi.org/10.1063/1.3428425 (3 pages) | Cited 1 time

Online Publication Date: 12 May 2010

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Neutron inelastic scattering has been used to measure the magnetic excitations as a function of applied magnetic field in an antiferromagnetically coupled Gd/Y superlattice. The excitations were measured along the c-axis, which is parallel to the normal of the interfaces and the sample growth direction. Dispersive spin waves were unambiguously detected on the application of a magnetic field. The spin waves are shown to renormalize with field following a basic model drawn from standard spin wave theory. The model required no free parameters aside from an initial amplitude.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Ee Antiferromagnetics
75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance

Simulation of magnetization switching by electric-field manipulation of magnetic anisotropy

D. Chiba, Y. Nakatani, F. Matsukura, and H. Ohno

Appl. Phys. Lett. 96, 192506 (2010); http://dx.doi.org/10.1063/1.3428959 (3 pages) | Cited 10 times

Online Publication Date: 12 May 2010

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Electrical anisotropy modulation was recently observed in ferromagnetic semiconductors and metals. The authors have investigated magnetization switching through magnetic anisotropy modulation induced by external electric field by means of simulation. Macrospin simulation using Landau–Lifshitz–Gilbert equation shows that switching is possible by controlling magnetic anisotropy for appropriate sets of parameters. The condition for quasistatic magnetization switching is also presented, in which magnetization direction is determined to minimize the magnetic free energy.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials

Tunnel magnetoresistance properties and film structures of double MgO barrier magnetic tunnel junctions

H. D. Gan, S. Ikeda, W. Shiga, J. Hayakawa, K. Miura, H. Yamamoto, H. Hasegawa, F. Matsukura, T. Ohkubo, K. Hono, and H. Ohno

Appl. Phys. Lett. 96, 192507 (2010); http://dx.doi.org/10.1063/1.3429594 (3 pages) | Cited 14 times

Online Publication Date: 13 May 2010

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The authors fabricated double MgO barrier magnetic tunnel junctions (MTJs) with 3-nm-thick Co40Fe40B20 free layer. When annealed at 350 °C, tunnel magnetoresistance (TMR) ratio at room temperature was 130%, much lower than that (297%) of single MgO barrier MTJs processed and annealed under the same condition. The middle CoFeB free layer sandwiched between the two MgO barriers was found to be mostly amorphous. Replacement of the Co40Fe40B20 free layer by a highly oriented Co50Fe50 layer and a composite Co50Fe50/Co40Fe40B20 layer led to the enhanced TMR ratios up to 165% and 212% at annealing temperature of 350 °C, respectively.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.Pq Other materials
81.40.Gh Other heat and thermomechanical treatments
81.40.Rs Electrical and magnetic properties related to treatment conditions

Current-induced switching of magnetic vortex core in ferromagnetic elliptical disks

Keisuke Yamada, Shinya Kasai, Yoshinobu Nakatani, Kensuke Kobayashi, and Teruo Ono

Appl. Phys. Lett. 96, 192508 (2010); http://dx.doi.org/10.1063/1.3428792 (3 pages) | Cited 3 times

Online Publication Date: 13 May 2010

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We report the experimental observation and micromagnetics simulation of the current-induced switching of the magnetic vortex core in ferromagnetic elliptical disks. We found that the critical current density required for the core switching depends on the relative alignment between the current direction and the elliptical axes of the disk. The micromagnetics simulation results qualitatively reproduce the experimental findings, suggesting that the vortex core displacement induced by the current plays a significant role for the core switching rather than the core velocity.
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85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)

Nonlocal injection of spin current into a superconducting Nb wire

K. Ohnishi, T. Kimura, and Y. Otani

Appl. Phys. Lett. 96, 192509 (2010); http://dx.doi.org/10.1063/1.3427483 (3 pages) | Cited 1 time

Online Publication Date: 14 May 2010

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Pure spin current injection into a superconductive Nb was demonstrated experimentally by employing a nonlocal spin absorption technique in a multiterminal lateral structure. From the reduction in spin signals, we found the absorption efficiency remained almost unchanged even after superconducting transition. The Nb/Cu interface properties were also complementarily examined by using a Nb/Cu/Nb junction incorporated in the same device, revealing superconductivity below the transition temperature. These experimental results support that the pure spin current can be absorbed into a superconductive Nb wire with almost the same efficiency as in a normal state.
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84.71.Mn Superconducting wires, fibers, and tapes
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
85.25.Cp Josephson devices
72.25.-b Spin polarized transport
74.25.F- Transport properties

Controllable magnetic property of SiC by anion-cation codoping

Hui Pan, Yong-Wei Zhang, Vivek Shenoy, and Huajian Gao

Appl. Phys. Lett. 96, 192510 (2010); http://dx.doi.org/10.1063/1.3428428 (3 pages) | Cited 5 times

Online Publication Date: 14 May 2010

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We present that the magnetic property of SiC can be controlled by anion-cation codoping based on first-principles calculations. The anion-cation codoped SiC can be either ferromagnetic or antiferromagnetic by controlling the codoping configurations. The Ferromagnetic SiC with a high exchange energy can be achieved by nitrogen-transition metal (TM: Cr, Mn, Fe, and Co) codoping, while oxygen-TM codoped SiC is antiferromagnetic or non-magnetic, regardless of whether TM-doped SiC is ferromagnetic, antiferromagnetic, or nonmagnetic. The ferromagnetism was attributed to carrier-mediated interactions because of the coupling between the spin-polarized d and p electrons.
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75.30.Et Exchange and superexchange interactions
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Ee Antiferromagnetics
61.72.up Other materials
75.76.+j Spin transport effects
72.25.Dc Spin polarized transport in semiconductors
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