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16 May 2011

Volume 98, Issue 20, Articles (20xxxx)

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Appl. Phys. Lett. 98, 201101 (2011); http://dx.doi.org/10.1063/1.3590716 (3 pages)

Martynas Beresna, Mindaugas Gecevičius, Peter G. Kazansky, and Titas Gertus
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Field- and current-induced domain-wall motion in permalloy nanowires with magnetic soft spots

Andreas Vogel, Sebastian Wintz, Theo Gerhardt, Lars Bocklage, Thomas Strache, Mi-Young Im, Peter Fischer, Jürgen Fassbender, Jeffrey McCord, and Guido Meier

Appl. Phys. Lett. 98, 202501 (2011); http://dx.doi.org/10.1063/1.3590267 (3 pages) | Cited 1 time

Online Publication Date: 16 May 2011

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We study field- and current-induced domain-wall motion in permalloy nanowires containing a square-shaped magnetically softened region. Implantation of chromium ions is used to induce pinning sites via a local reduction in the saturation magnetization. Micromagnetic simulations, magnetic transmission soft x-ray microscopy, and electrical measurements are employed to characterize the pinning potential which significantly differs for transverse and vortex walls. Reliable domain-wall depinning from a so-called magnetic soft spot by single current pulses is observed. This demonstrates the suitability of these pinning sites for applications.
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75.75.-c Magnetic properties of nanostructures
73.63.-b Electronic transport in nanoscale materials and structures
72.15.Gd Galvanomagnetic and other magnetotransport effects
61.72.up Other materials
75.60.Ch Domain walls and domain structure
75.47.Np Metals and alloys

Electronic tuning of magnetic permeability in Co2Z hexaferrite toward high frequency electromagnetic device miniaturization

Yajie Chen, Andrew Daigle, Trifon Fitchorov, Bolin Hu, Michael Geiler, Anton Geiler, C. Vittoria, and V. G. Harris

Appl. Phys. Lett. 98, 202502 (2011); http://dx.doi.org/10.1063/1.3590771 (3 pages)

Online Publication Date: 17 May 2011

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The magnetic and magnetostriction properties of Z-type cobalt-doped barium hexaferrite with perpendicular c-axis crystallographic texture are presented. The hexaferrite was utilized as a component in Co2Z/lead magnesium niobate-lead titanate multiferroic heterostructures whose tunability of permeability with electric field in terms of ferromagnetic resonance shift was supported by experiments and theoretical calculation. A permeability change of 16% was measured by an induced magnetic field of 38 Oe under the application of 6 kV/cm of electric field. These findings lay the foundation for the application of Z-type hexaferrites in tunable rf and microwave devices valued for sending, receiving, and manipulating electromagnetic signals.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.80.+q Magnetomechanical effects, magnetostriction
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.80.-e Ferroelectricity and antiferroelectricity
75.50.Gg Ferrimagnetics

Superconducting quantum interference device as a near-quantum-limited amplifier for the axion dark-matter experiment

D. Kinion and John Clarke

Appl. Phys. Lett. 98, 202503 (2011); http://dx.doi.org/10.1063/1.3583380 (3 pages) | Cited 2 times

Online Publication Date: 17 May 2011

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We characterized a microstrip superconducting quantum interference device amplifier (MSA) as a function of frequency and temperature. At 40 mK, with optimal current and flux biases, the maximum gain of 20.4 dB was at 620 MHz; the bandwidth was 21 MHz. The minimum noise temperature TN = 48±5 mK occurred at 612 MHz, slightly below the frequency of maximum gain. This value of TN is within a factor of 1.6 of the quantum limit TQ = hf/kB (f is frequency) for a linear, phase-preserving amplifier. Incorporating the MSA into the axion detector at the University of Washington will increase the scan rate by two to three orders of magnitude.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.30.Le Amplifiers

Quantum well thickness dependence of Rashba spin–orbit coupling in the InAs/InGaAs heterostructure

Tae Young Lee, Joonyeon Chang, Mark C. Hickey, Hyun Cheol Koo, Hyung-jun Kim, Suk Hee Han, and Jagadeesh S. Moodera

Appl. Phys. Lett. 98, 202504 (2011); http://dx.doi.org/10.1063/1.3589812 (3 pages)

Online Publication Date: 18 May 2011

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We have investigated the quantum well thickness dependence of spin–orbit coupling in InAs/InGaAs heterostructures. The beat patterns of the oscillatory magnetoresistance were measured to determine the magnitude of the parameter of an inverted type InAs quantum well structures with the thicknesses ranging from 2 to 7 nm. The band energies, electronic charge distribution, and Rashba spin–orbit coupling parameter of the structure were calculated using a self-consistent field method and a k⋅P perturbation scheme. The magnitude of the parameter increases with decreasing the InAs quantum well thickness. Comparison with the calculated data revealed that the increase in the spin–orbit interaction parameter is due to the stronger penetration of the wave function envelope into the barriers where more pronounced band bending and barrier asymmetry occur in both the conduction and valence bands.
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71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.21.Fg Quantum wells
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
72.20.My Galvanomagnetic and other magnetotransport effects

Magnetic order near 270 K in mineral and synthetic Mn2FeSbO6 ilmenite

R. Mathieu, S. A. Ivanov, G. V. Bazuev, M. Hudl, P. Lazor, I. V. Solovyev, and P. Nordblad

Appl. Phys. Lett. 98, 202505 (2011); http://dx.doi.org/10.1063/1.3593194 (3 pages)

Online Publication Date: 19 May 2011

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The structural and magnetic properties of Mn2FeSbO6 single-crystalline mineral and ceramic samples synthesized under thermobaric treatment have been investigated, and compared to theoretical predictions based on first-principles electronic structure calculations. This ilmenite system displays a sharp magnetic transition just below the room temperature related to a ferrimagnetic ordering of the Mn2+ and Fe3+ cations, which makes Mn2FeSbO6 a promising candidate for designing functional magnetic materials.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
71.20.Ps Other inorganic compounds
61.66.Fn Inorganic compounds
75.50.Gg Ferrimagnetics
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Tunability of the critical-current density in superconductor-ferromagnet hybrids

Nuria Del-Valle, Carles Navau, Alvaro Sanchez, and Du-Xing Chen

Appl. Phys. Lett. 98, 202506 (2011); http://dx.doi.org/10.1063/1.3591971 (3 pages) | Cited 1 time

Online Publication Date: 19 May 2011

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Important modifications on the magnetization loops of the superconductor have been observed in superconductor-ferromagnet hybrids due to the effects of the ferromagnetic components, which can be used for tuning the superconductor critical-current density Jc to desirable values. Here, a model based on an energy minimization procedure is presented to analyze the complex interaction between the superconductor and the ferromagnets. We show how the geometry and orientation of the ferromagnets can be chosen for shifting the position of the peaks appearing in the magnetization to positive or negative applied fields, and, consequently, to tune Jc in superconductor-ferromagnet hybrids.
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74.25.Sv Critical currents
74.25.Ha Magnetic properties including vortex structures and related phenomena
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