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30 Oct 2006

Volume 89, Issue 18, Articles (18xxxx)

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Appl. Phys. Lett. 89, 181101 (2006); http://dx.doi.org/10.1063/1.2372737 (3 pages)

Z. D. Gao, S. N. Zhu, Shih-Yu Tu, and A. H. Kung
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Unusual magnetic and transport properties of oxygen deficient Sr2Fe1−xCoxMoO6−d

Hong Chang, Mar García-Hernández, and Jose Antonio Alonso

Appl. Phys. Lett. 89, 182501 (2006); http://dx.doi.org/10.1063/1.2360206 (3 pages) | Cited 2 times

Online Publication Date: 30 October 2006

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In the title compounds the oxygen voids have a significant influence over the transport properties, compared with the parent stoichiometric compounds (Sr2FeMoO6 and Sr2CoMoO6) where the oxygen defects have little impact on the crystallographic and magnetic properties. For Sr2FeMoO6−d and Sr2Fe0.95Co0.05MoO6−d, the oxygen voids simply decrease the magnetoresistance (MR) without altering the contours, and for x ≥ 0.1 at the expense of the decreased low field MR, the oxygen voids enhance MR at high applied field, which is 6%–8% larger than the parent compounds for 0.2 ⩽ x ⩽ 0.7. Remarkably enough, the antiferromagnetic Sr2Fe0.1Co0.9MoO6−d exhibits record negative magnetoresistance ratio MR = ((R(H,T)−R(0,T))/R(0,T))×100% as high as 99%.
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72.20.My Galvanomagnetic and other magnetotransport effects
75.47.Pq Other materials
75.50.Ee Antiferromagnetics
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Magnetic anisotropy study of ion-beam synthesized cobalt nanocrystals

J.-K. Lee, M. F. Hundley, J. D. Thompson, R. K. Schulze, H. S. Jung, J. A. Valdez, M. Nastasi, and X. Zhang

Appl. Phys. Lett. 89, 182502 (2006); http://dx.doi.org/10.1063/1.2364176 (3 pages) | Cited 3 times

Online Publication Date: 30 October 2006

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The magnetic properties of Co nanocrystals in crystalline Al2O3 and amorphous SiO2 are investigated. In contrast to the SiO2 matrix, the Al2O3 matrix provides higher magnetic anisotropy and coercive field for Co nanocrystals. Using x-ray photoemission spectroscopy, it is found that a CoAl2O4 layer forms in Co implanted region. Transmission electron microscopy shows that this CoAl2O4 layer is grown epitaxially around Co nanocrystals. The higher coercive field of the Co nanocrystals in Al2O3 is attributed to the presence of antiferromagnetic CoAl2O4 layers.
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75.50.Cc Other ferromagnetic metals and alloys
75.50.Ee Antiferromagnetics
75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Hyperfine splitting from magnetic boride domains embedded in Fe–Co–Ni–Al–B–Si alloy

Hsin-Fu Kuo, Wei Chin, Tung-Wen Cheng, Wen-Kuang Hsu, and Jien-Wei Yeh

Appl. Phys. Lett. 89, 182503 (2006); http://dx.doi.org/10.1063/1.2372746 (3 pages) | Cited 8 times

Online Publication Date: 31 October 2006

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Fe–Co–Ni–Al–B–Si alloy shows permeability at the gigahertz range and it is proposed that the underlying mechanism involves hyperfine splitting arising, from embedded boride domains.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
76.30.-v Electron paramagnetic resonance and relaxation
75.60.Ch Domain walls and domain structure
75.50.Bb Fe and its alloys

Spin-polarized conduction in oxide magnetic tunnel junctions with magnetic and nonmagnetic insulating barrier layers

L. M. B. Alldredge, R. V. Chopdekar, B. B. Nelson-Cheeseman, and Y. Suzuki

Appl. Phys. Lett. 89, 182504 (2006); http://dx.doi.org/10.1063/1.2372765 (3 pages) | Cited 10 times

Online Publication Date: 31 October 2006

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Epitaxial magnetic tunnel junctions with electrodes of spinel-structure Fe3O4 and perovskite La0.7Sr0.3MnO3 have been fabricated and characterized. Spinel barrier layers of magnetic FeGa2O4 and nominally nonmagnetic Mg2TiO4 were used to provide a good interface with the more sensitive Fe3O4 electrode interface. Junction magnetoresistances (JMRs) of up to −11% at 60 K and −26% at 70 K were observed for FeGa2O4 and Mg2TiO4 barrier junctions, respectively. The JMR bias dependence and junction resistance versus temperature data indicate that a majority of the junctions are dominated by elastic tunneling below about 50 mV and by inelastic hopping through the barrier at higher bias.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.Pq Other materials
72.25.Mk Spin transport through interfaces

Tunable pinning in superconducting films with magnetic microloops

A. V. Silhanek, W. Gillijns, V. V. Moshchalkov, V. Metlushko, and B. Ilic

Appl. Phys. Lett. 89, 182505 (2006); http://dx.doi.org/10.1063/1.2374798 (3 pages) | Cited 12 times

Online Publication Date: 31 October 2006

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The authors study the flux pinning properties of superconductor/magnetic microring lattice hybrid structures. The used open triangular micromagnets represent an eightfold degree of freedom system, with six polarized and two flux-closure possible states. By conveniently choosing the magnetic state of the underlying rings, it is possible to induce different pinning potentials. They show that the magnetic vortex state with minimum stray field produces a weaker pinning in comparison with the polarized states.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)

Magnetoelectric coupling in epitaxial CoFe2O4 on BaTiO3

R. V. Chopdekar and Y. Suzuki

Appl. Phys. Lett. 89, 182506 (2006); http://dx.doi.org/10.1063/1.2370881 (3 pages) | Cited 23 times

Online Publication Date: 31 October 2006

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The authors have synthesized epitaxial CoFe2O4 films on piezoelectric BaTiO3 single crystal substrates as a model magnetoelectric system. The BaTiO3 substrate provides a surface lattice that can be dynamically changed in an attempt to alter the strain state and hence the magnetization of the CoFe2O4 film. Magnetization measurements indicate that the magnetic anisotropy of CoFe2O4 is dominated by compressive epitaxial strain effects and can be understood in terms of the symmetry of the substrate surface unit cell.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.60.Bs Mechanical and acoustical properties

Large magnetic entropy changes in the Ni45.4Mn41.5In13.1 ferromagnetic shape memory alloy

Z. D. Han, D. H. Wang, C. L. Zhang, S. L. Tang, B. X. Gu, and Y. W. Du

Appl. Phys. Lett. 89, 182507 (2006); http://dx.doi.org/10.1063/1.2385147 (3 pages) | Cited 88 times

Online Publication Date: 31 October 2006

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The inverse magnetocaloric effect associated with the martensitic transition in the Ni45.4Mn41.5In13.1 Heusler alloy is reported. A large positive magnetic entropy change of 8 J/kg K under a low magnetic field of 10 kOe is found near the martensitic transition temperature. This change originates from the first-order transition from a low-temperature weak-magnetic martensitic phase to a high-temperature ferromagnetic austenitic phase. The large low-field magnetic entropy change indicates a great potential of Ni–Mn–In alloys as working materials for magnetic refrigeration in a wide temperature range.
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75.50.Cc Other ferromagnetic metals and alloys
75.30.Sg Magnetocaloric effect, magnetic cooling
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions

Growth of [110] La2/3Sr1/3MnO3–YBa2Cu3O7 heterostructures

Soumen Mandal, Saurabh K. Bose, Rajeev Sharma, R. C. Budhani, Prahallad Padhan, and Wilfrid Prellier

Appl. Phys. Lett. 89, 182508 (2006); http://dx.doi.org/10.1063/1.2374692 (3 pages) | Cited 2 times

Online Publication Date: 1 November 2006

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YBa2Cu3O7–La2/3Sr1/3MnO3 heterostructures of [110] orientation are grown to allow direct injection of spin polarized holes from the La2/3Sr1/3MnO3 into the CuO2 superconducting planes. The magnetic response of the structure at T<Tsc shows both diamagnetic and ferromagnetic moments with [001] direction as magnetic easy axis. While the superconducting transition temperature (Tsc) of these structures is sharp (ΔTsc ≃ 2.5 K), the critical current density (Jc) follows a dependence of the type Jc = Jo(1−T/Tsc)3/2 with highly suppressed Jo( ≃ 2×104 A/cm2), indicating strong pair breaking effects of the ferromagnetic boundary.
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81.15.Fg Pulsed laser ablation deposition
74.72.-h Cuprate superconductors
74.25.Sv Critical currents
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.F- Transport properties

Spin polarization of oxygen atoms in ferromagnetic Co-doped rutile TiO2

A. Nefedov, N. Akdogan, H. Zabel, R. I. Khaibullin, and L. R. Tagirov

Appl. Phys. Lett. 89, 182509 (2006); http://dx.doi.org/10.1063/1.2378398 (3 pages) | Cited 12 times

Online Publication Date: 1 November 2006

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Of central interest in the research of dilute magnetic semiconductors is the coupling mechanism leading to a ferromagnetic ground state. Using x-ray resonant magnetic scattering, we have analyzed the element specific magnetic hysteresis curves of Co, Ti, and oxygen in Co-doped TiO2 synthesized by ion implantation. Magnetic dichroism was observed at the Co L2,3 edges, as well as at the O K edge, indicative of a spin polarization of oxygen atoms in the TiO2 host matrix. The hysteretic shapes and the coercive field values measured at the Co L3 and O K edges are identical (1.9 kOe at 30 K).
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75.50.Pp Magnetic semiconductors
72.25.Dc Spin polarized transport in semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Cc Other ferromagnetic metals and alloys
61.72.up Other materials
61.80.Jh Ion radiation effects

Observation of large magnetoresistance of magnetic Heusler alloy Ni50Mn36Sn14 in high magnetic fields

Keiichi Koyama, Hironari Okada, Kazuo Watanabe, Takeshi Kanomata, Ryosuke Kainuma, Wataru Ito, Katsunari Oikawa, and Kiyohito Ishida

Appl. Phys. Lett. 89, 182510 (2006); http://dx.doi.org/10.1063/1.2374868 (3 pages) | Cited 78 times

Online Publication Date: 2 November 2006

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The magnetic and electrical properties on magnetic Heusler alloy Ni50Mn36Sn14 were studied in magnetic fields up to 18 T in 4.2–270 K temperature range. It was found that at the vicinity of 160 K the resistivity jump of 46% is accompanied by the magnetic phase transition. Furthermore, the large magnetoresistance effect of 50% by the magnetic field induced magnetic phase transition was observed.
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75.47.Np Metals and alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)

Atomically controlled molecular beam epitaxy of ferromagnetic silicide Fe3Si on Ge

T. Sadoh, M. Kumano, R. Kizuka, K. Ueda, A. Kenjo, and M. Miyao

Appl. Phys. Lett. 89, 182511 (2006); http://dx.doi.org/10.1063/1.2378399 (3 pages) | Cited 21 times

Online Publication Date: 2 November 2006

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Low-temperature (60 °C) molecular beam epitaxy (MBE) of Fe3Si layers on Ge substrates was investigated. From x-ray diffraction and transmission electron microscopy measurements, it was shown that Fe3Si layers including the DO3 type were epitaxially grown on Ge(110) and Ge(111), while polycrystal Fe3Si was formed on Ge(100). Although the Fe3Si/Ge(110) interface was slightly rough ( ∼ 1 nm), the Fe3Si/Ge(111) interface was atomically flat. Such atomically controlled MBE of Fe3Si on the Ge(111) substrate can be employed to realize Ge channel spin transistors, which can be integrated with Si large-scale integrated circuits.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys
72.25.Mk Spin transport through interfaces

Epitaxial growth and the magnetic properties of orthorhombic YTiO3 thin films

S. C. Chae, Y. J. Chang, S. S. A. Seo, T. W. Noh, D.-W. Kim, and C. U. Jung

Appl. Phys. Lett. 89, 182512 (2006); http://dx.doi.org/10.1063/1.2374850 (3 pages) | Cited 6 times

Online Publication Date: 3 November 2006

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High-quality YTiO3 thin films were grown on LaAlO3 (110) substrates at low oxygen pressures ( ⩽ 10−8 Torr) using pulsed laser deposition. The in-plane asymmetric atomic arrangements at the substrate surface allowed the authors to grow epitaxial YTiO3 thin films, which have an orthorhombic crystal structure with quite different a- and b-axis lattice constants. The YTiO3 film exhibited a clear ferromagnetic transition at 30 K with a saturation magnetization of about 0.7μB/Ti. The magnetic easy axis was found to be along the [1−10] direction of the substrate, which differs from the single crystal easy axis direction, i.e., [001].
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75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
81.05.-t Specific materials: fabrication, treatment, testing, and analysis
81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth

Switching of magnetic domains in Permalloy microstructures using two-dimensional electron gas

A. Belkin, J. Fedor, P. Pankowski, M. Iavarone, V. Novosad, G. Karapetrov, V. Cambel, D. Gregušová, and R. Kúdela

Appl. Phys. Lett. 89, 182513 (2006); http://dx.doi.org/10.1063/1.2378488 (3 pages)

Online Publication Date: 3 November 2006

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The authors demonstrate the ability to monitor and alter the magnetization state of microscopic Permalloy element deposited on the active area of a two-dimensional electron gas (2DEG) Hall probe using the current through the 2DEG. Magnetic force microscopy imaging shows the exact magnetization state of the Permalloy thin film ellipse at different applied magnetic fields. Recorded Hall voltage signal provides information on local magnetization of the ferromagnetic element at the same time. Application of short, but intense current pulses through the Hall probe changes the magnetization state of the Permalloy ellipse.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys
75.60.Ch Domain walls and domain structure
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.20.My Galvanomagnetic and other magnetotransport effects

Rapid single flux quantum devices with selective dissipation for quantum information processing

J. Hassel, P. Helistö, H. Seppä, J. Kunert, L. Fritzsch, and H.-G. Meyer

Appl. Phys. Lett. 89, 182514 (2006); http://dx.doi.org/10.1063/1.2382733 (3 pages) | Cited 6 times

Online Publication Date: 3 November 2006

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The authors study the frequency dependent damping in rapid single flux quantum (RSFQ) circuits as means to reduce dissipation and consequent decoherence in RSFQ/qubit circuits. They show by simulations and experiments that stable RSFQ operation can be achieved by shunting the Josephson junctions with an RC circuit instead of a plain resistor. The authors derive criteria for the stability of such an arrangement and discuss the effect on decoherence.
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03.67.Lx Quantum computation architectures and implementations
85.25.Cp Josephson devices
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