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physica status solidi (RRL) - Rapid Research Letters

Cover image for Vol. 5 Issue 12

Special Issue: Focus on Spintronics and Spin Physics

December 2011

Volume 5, Issue 12

Pages A117–A128, 413–452

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Issue Information
    4. Back Cover
    5. Preface
    6. Contents
    7. NEW IN pss
    8. Conference calendar
    9. Frontispiece
    10. Review@RRL
    11. Rapid Research Letters
    12. Information for authors
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      Cover Picture: Electronic structure of EuO spin filter tunnel contacts directly on silicon (Phys. Status Solidi RRL 12/2011)

      C. Caspers, M. Müller, A. X. Gray, A. M. Kaiser, A. Gloskovskii, C. S. Fadley, W. Drube and C. M. Schneider

      Article first published online: 16 NOV 2011 | DOI: 10.1002/pssr.201190027

      Thumbnail image of graphical abstract

      Establishing magnetic oxides as spin-selective tunnel barriers on mainstream semiconductors opens up a promising route towards highly efficient spin injection and detection. Europium oxide (EuO) is the only magnetic oxide predicted to be stable in direct contact with silicon. A throughout hard X-ray photoemission spectroscopy study (see the Letter by Caspers et al. on pp. 441–443) reveals the nearly ideal stoichiometry of EuO “spin filter” tunnel barriers grown by Oxide-MBE, with no silicon oxide or silicide formation being observed at the EuO/Si interface. This result clearly demonstrates the successful integration of a magnetic oxide tunnel barrier with silicon, opening up the future integration of magnetic oxides into functional spintronics devices.

  2. Issue Information

    1. Top of page
    2. Cover Picture
    3. Issue Information
    4. Back Cover
    5. Preface
    6. Contents
    7. NEW IN pss
    8. Conference calendar
    9. Frontispiece
    10. Review@RRL
    11. Rapid Research Letters
    12. Information for authors
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      Issue Information: Phys. Status Solidi RRL 12/2011

      Article first published online: 16 NOV 2011 | DOI: 10.1002/pssr.201190028

  3. Back Cover

    1. Top of page
    2. Cover Picture
    3. Issue Information
    4. Back Cover
    5. Preface
    6. Contents
    7. NEW IN pss
    8. Conference calendar
    9. Frontispiece
    10. Review@RRL
    11. Rapid Research Letters
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      Back Cover: Magnetic vortex excitation dependence on the magnetic free layer and size of spin-valve nanocontacts (Phys. Status Solidi RRL 12/2011)

      Moritz Eggeling, Theodoros Dimopoulos, Rudolf Heer and Hubert Brückl

      Article first published online: 16 NOV 2011 | DOI: 10.1002/pssr.201190029

      Thumbnail image of graphical abstract

      Eggeling et al. (pp. 435–437) investigated the size and magnetic free layer dependence of the vortex dynamics in relatively large spin-valve nanocontacts. A circular nano- contact confines the current flow through a spin-valve multilayer (upper cover image) incorporating a magnetic free layer and an unpinned artificial antiferromagnet as polarizer. Spin-torque driven magnetic vortex dynamics are observed in dependence on the magnetic properties, the contact size and the applied current, provoking microwave oscillations at zero external magnetic field. The oscillation spectra (lower image) show the evolution of single and multiple radio frequency modes as a function of the nanocontact size. These specific properties make spin-torque-driven devices suitable e.g. for nano-sized microwave sources, ultra-compact magnetic field sensors or fast and non-volatile magnetic memories.

  4. Preface

    1. Top of page
    2. Cover Picture
    3. Issue Information
    4. Back Cover
    5. Preface
    6. Contents
    7. NEW IN pss
    8. Conference calendar
    9. Frontispiece
    10. Review@RRL
    11. Rapid Research Letters
    12. Information for authors
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      Focus on Spintronics and Spin Physics (pages A117–A118)

      S. N. Piramanayagam, Jagadeesh Moodera, Russell Cowburn and Rachid Sbiaa

      Article first published online: 16 NOV 2011 | DOI: 10.1002/pssr.201150341

  5. Contents

    1. Top of page
    2. Cover Picture
    3. Issue Information
    4. Back Cover
    5. Preface
    6. Contents
    7. NEW IN pss
    8. Conference calendar
    9. Frontispiece
    10. Review@RRL
    11. Rapid Research Letters
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      Contents: Phys. Status Solidi RRL 12/2011 (pages A119–A123)

      Article first published online: 16 NOV 2011 | DOI: 10.1002/pssr.201150342

  6. NEW IN pss

    1. Top of page
    2. Cover Picture
    3. Issue Information
    4. Back Cover
    5. Preface
    6. Contents
    7. NEW IN pss
    8. Conference calendar
    9. Frontispiece
    10. Review@RRL
    11. Rapid Research Letters
    12. Information for authors
    1. You have free access to this content
  7. Conference calendar

    1. Top of page
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    3. Issue Information
    4. Back Cover
    5. Preface
    6. Contents
    7. NEW IN pss
    8. Conference calendar
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    10. Review@RRL
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      Conference calendar: Phys. Status Solidi RRL 12/2011 (page A125)

      Article first published online: 16 NOV 2011 | DOI: 10.1002/pssr.201150344

  8. Frontispiece

    1. Top of page
    2. Cover Picture
    3. Issue Information
    4. Back Cover
    5. Preface
    6. Contents
    7. NEW IN pss
    8. Conference calendar
    9. Frontispiece
    10. Review@RRL
    11. Rapid Research Letters
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      Frontispiece: Materials with perpendicular magnetic anisotropy for magnetic random access memory (Phys. Status Solidi RRL 12/2011)

      R. Sbiaa, H. Meng and S. N. Piramanayagam

      Article first published online: 16 NOV 2011 | DOI: 10.1002/pssr.201150345

      Thumbnail image of graphical abstract

      This Focus Issue on “Spintronics and Spin Physics” aims at taking a snapshot of ongoing diverse and high-level spin physics and nanomagnetism research trends. Spintronics has long achieved real-world application in hard-disk drives, and yet the topic literally got a new spin after the discovery of the spin-transfer torque effect which led to a revival of research on magnetic random access memories (MRAMs), magnetic logic devices, domain wall memories, etc.

      In their Review@RRL (pp. 413–419), R. Sbiaa, H. Meng, and S. N. Piramanayagam give an overview of the development of materials with perpendicular magnetic anisotropy that are crucial for MRAM and other spintronics applications. In particular, for a spin-transfer torque MRAM design the five conflicting criteria of high signal, low resistance, high thermal stability, low writing current, and CMOS integration need to be met, the so-called MRAM pentalemma.

  9. Review@RRL

    1. Top of page
    2. Cover Picture
    3. Issue Information
    4. Back Cover
    5. Preface
    6. Contents
    7. NEW IN pss
    8. Conference calendar
    9. Frontispiece
    10. Review@RRL
    11. Rapid Research Letters
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      Materials with perpendicular magnetic anisotropy for magnetic random access memory (pages 413–419)

      R. Sbiaa, H. Meng and S. N. Piramanayagam

      Article first published online: 4 OCT 2011 | DOI: 10.1002/pssr.201105420

      Thumbnail image of graphical abstract

      In this Review, the princple of spin-transfer torque magnetic random access memory (STT-MRAM) is explained: The magnetic tunnel junction device is sandwiched between two electrodes (cross-point architecture). The writing is based on spin torque effect and the reading on tunnelling magneto-resistive effect. In contrast to field-based MRAM, STT-MRAM does not require external magnetic field. Since STT-MRAM is scalable, the transistor scales down with the device size. Materials with perpendicular magnetic anisotropy (PMA) are being investigated for their use in STT-MRAM – multilayers such as Co/Pd and Co/Pt as well as FeCoB and future candidates such as FePt.

  10. Rapid Research Letters

    1. Top of page
    2. Cover Picture
    3. Issue Information
    4. Back Cover
    5. Preface
    6. Contents
    7. NEW IN pss
    8. Conference calendar
    9. Frontispiece
    10. Review@RRL
    11. Rapid Research Letters
    12. Information for authors
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      Reduction of switching time in pentalayer magnetic tunnel junctions with a composite-free layer (pages 420–422)

      Alexander Makarov, Viktor Sverdlov, Dmitry Osintsev and Siegfried Selberherr

      Article first published online: 12 SEP 2011 | DOI: 10.1002/pssr.201105376

      Thumbnail image of graphical abstract

      In this Letter the authors report a substantial decrease of the switching time in a pentalayer structure with a composite-free layer as compared to the pentalayer structure of similar dimensions with a monolithic free layer. The physical reasons for the switching time reduction at the same current density are discussed.

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      Heat-driven spin currents on large scales (pages 423–425)

      Sylvain D. Brechet and Jean-Philippe Ansermet

      Article first published online: 20 JUN 2011 | DOI: 10.1002/pssr.201105180

      Thumbnail image of graphical abstract

      Brechet and Ansermet show that a three-current model of heat, spin-up and spin-down currents predicts the spin polarisation current to exist on large scales and to be proportional to the temperature gradient, corresponding to a spin Soret effect. They establish the existence of the spin current driven by a heat current over large distances in the absence of a charge current and at equilibrium of the spin channels. Thus, a heat current may also affect the magnetisation.

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      Tailoring the growth of L10-FePt for spintronics applications (pages 426–428)

      Taiebeh Tahmasebi, Seidikkurippu N. Piramanayagam, Rachid Sbiaa, Hang Khume Tan, Randall Law, Sunny Lua and Tow Chong Chong

      Article first published online: 17 OCT 2011 | DOI: 10.1002/pssr.201105379

      Thumbnail image of graphical abstract

      Ordered L10-FePt with large magnetocrystalline anisotropy (Ku) and high saturation magnetization (Ms) enables potential scaling of spintronic devices down to 5 nm. FePt films need to be smooth and possess good (001) texture in order to achieve the desired properties for spintronics applications. This Letter focuses on tailoring of L10-FePt growth for such applications. The L10-FePt magnetic layers deposited on Pd seed layers exhibit large ordering parameter, smoothness and strong perpendicular magnetic anisotropy.

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      Magnetism and magnetotransport in sputtered Co-doped FeSi films (pages 429–431)

      Sophie A. Morley, Nicholas A. Porter and Christopher H. Marrows

      Article first published online: 7 OCT 2011 | DOI: 10.1002/pssr.201105386

      Thumbnail image of graphical abstract

      Microelectronics manufacturing relies on planar processing for which thin films are needed. Sputtered films of cobalt-doped iron monosolicide have been fabricated and characterised. The non-centrosymmetric ε-phase is the predominant form of the material after annealing. It shows similar magnetic and magnetotransport properties to bulk single crystals in spite of the inherent disorder in a thin film. This includes a ratio of magnetic moment to carrier density of approximately unity, suggesting a high spin-polarisation in this silicon-based material.

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      High frequency operation of a spin-torque oscillator at low field (pages 432–434)

      S. M. Mohseni, S. R. Sani, J. Persson, T. N. Anh Nguyen, S. Chung, Ye. Pogoryelov and Johan Åkerman

      Article first published online: 26 OCT 2011 | DOI: 10.1002/pssr.201105375

      Thumbnail image of graphical abstract

      In this Letter the authors demonstrate a nanocontact spin-torque oscillator (STO) based on an orthogonal spin-valve architecture with an in-plane Co polarizer and an out-of-plane Co/Ni multilayer free layer. High frequency operation at low external fields is achieved by tailoring the Co/Ni layer properties to increase the strength of the perpendicular magnetic anisotropy, while simultaneously reducing the saturation magnetization.

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      Magnetic vortex excitation dependence on the magnetic free layer and size of spin-valve nanocontacts (pages 435–437)

      Moritz Eggeling, Theodoros Dimopoulos, Rudolf Heer and Hubert Brückl

      Article first published online: 19 SEP 2011 | DOI: 10.1002/pssr.201105374

      Thumbnail image of graphical abstract

      Spin-torque-driven vortex-oscillators can be applied as nano-sized microwave sources, ultra-compact magnetic field sensors or in fast and non-volatile magnetic memories. This Letter demonstrates the dependence of vortex dynamics on the free layer and the size of relatively large spin-valve nanocontacts, incorporating an unpinned artificial antiferromagnet. Nucleation current density, multiple mode excitation and magnetic field dependence are specifically addressed.

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      Ferrimagnetic ZnFe2O4 thin films on SrTiO3 single crystals with highly tunable electrical conductivity (pages 438–440)

      Michael Lorenz, Matthias Brandt, Katja Mexner, Kerstin Brachwitz, Michael Ziese, Pablo Esquinazi, Holger Hochmuth and Marius Grundmann

      Article first published online: 13 OCT 2011 | DOI: 10.1002/pssr.201105359

      Thumbnail image of graphical abstract

      Within the current search for spintronic materials with spin polarized conductivity, zinc ferrite (ZnFe2O4) thin films grown on SrTiO3(001) and (111) single crystals are highly promising as magnetic semiconducting electrode in advanced all-oxide tunnel junctions and field effect transistors, as well as insulating barrier in spin filters. This is due to the highly tunable electrical conductivity coupled with high saturation magnetization.

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      Electronic structure of EuO spin filter tunnel contacts directly on silicon (pages 441–443)

      C. Caspers, M. Müller, A. X. Gray, A. M. Kaiser, A. Gloskovskii, C. S. Fadley, W. Drube and C. M. Schneider

      Article first published online: 12 OCT 2011 | DOI: 10.1002/pssr.201105403

      Thumbnail image of graphical abstract

      Hard X-ray photoemission spectroscopy reveals the nearly ideal stoichiometry of EuO spin filter tunnel barriers grown directly on silicon, and the absence of silicon oxide formation at the EuO/Si interface. These results demonstrate the successful integration of a magnetic oxide tunnel barrier with silicon, paving the way for the future integration of magnetic oxides into functional spintronics devices.

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      A spin-calorics device based on La0.7Sr0.3MnO3/SrRuO3 superlattices (pages 444–446)

      M. Ziese

      Article first published online: 2 AUG 2011 | DOI: 10.1002/pssr.201105318

      Thumbnail image of graphical abstract

      In this Letter a spin-caloric device is proposed that consists of a wedge-shaped La0.7Sr0.3MnO3/SrRuO3 superlattice (SL). Studies of SLs with various layer thicknesses show that the magnetic work can be strongly influenced by the engineering of the crystalline symmetry or the use of exchange biasing. A SL wedge in a rapidly varying magnetic field should therefore support a self-sustained Seebeck effect.

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      Defect engineering of room-temperature ferromagnetism of carbon-doped ZnO (pages 447–449)

      H. S. Hsu, Y. Tung, Y. J. Chen, M. G. Chen, J. S. Lee and S. J. Sun

      Article first published online: 12 SEP 2011 | DOI: 10.1002/pssr.201105395

      Thumbnail image of graphical abstract

      Room-temperature ferromagnetism observed in an air-annealed C:ZnO sample was associated with a ferromagnetic magnetic circular dichroism peak. This is related to the loss of carbon and the creation of defects in an air-annealed C:ZnO film by the reaction between carbon dopants and oxygen. In this Letter the authors suggest that a combination of carbon doping and a suitable post-annealing treatment has a strong impact on the defect-mediated ferromagnetism of C:ZnO.

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      Indirect interaction of magnetic domain walls (pages 450–452)

      N. Sedlmayr, V. K. Dugaev, M. Inglot and J. Berakdar

      Article first published online: 23 AUG 2011 | DOI: 10.1002/pssr.201105368

      Thumbnail image of graphical abstract

      In this Letter the authors calculate the carrier-mediated interaction between domain walls in a ferromagnetic strip. The result is an oscillating function of both the interdomain wall distance and their relative orientations. Sedlmayr et al. go on to show how this can give rise to spiralling domain wall orientations in a strip. Such an interaction can have consequences for any tightly packed wire of domain walls.

  11. Information for authors

    1. Top of page
    2. Cover Picture
    3. Issue Information
    4. Back Cover
    5. Preface
    6. Contents
    7. NEW IN pss
    8. Conference calendar
    9. Frontispiece
    10. Review@RRL
    11. Rapid Research Letters
    12. Information for authors
    1. You have free access to this content

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