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25 Jun 2012

Volume 100, Issue 26, Articles (26xxxx)

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Appl. Phys. Lett. 100, 261104 (2012); http://dx.doi.org/10.1063/1.4711253 (4 pages)

Marcelo Davanço, Jun Rong Ong, Andrea Bahgat Shehata, Alberto Tosi, Imad Agha, Solomon Assefa, Fengnian Xia, William M. J. Green, Shayan Mookherjea, and Kartik Srinivasan
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Temperature-driven nucleation of ferromagnetic domains in FeRh thin films

C. Baldasseroni, C. Bordel, A. X. Gray, A. M. Kaiser, F. Kronast, J. Herrero-Albillos, C. M. Schneider, C. S. Fadley, and F. Hellman

Appl. Phys. Lett. 100, 262401 (2012); http://dx.doi.org/10.1063/1.4730957 (5 pages) | Cited 1 time

Online Publication Date: 25 June 2012

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The evolution of ferromagnetic (FM) domains across the temperature-driven antiferromagnetic (AF) to FM phase transition in uncapped and capped epitaxial FeRh thin films was studied by x-ray magnetic circular dichroism and photoemission electron microscopy. The coexistence of the AF and FM phases was evidenced across the broad transition and the different stages of nucleation, growth, and coalescence were directly imaged. The FM phase nucleates into single domain islands and the width of the transition of an individual nucleus is sharper than that of the transition in a macroscopic average.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
78.20.Ls Magneto-optical effects
78.66.Bz Metals and metallic alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Bb Fe and its alloys
75.70.Ak Magnetic properties of monolayers and thin films

Magnetic Schottky diode exploiting spin polarized transport in Co/p-Si heterostructure

A. Sarkar, R. Adhikari, and A. K. Das

Appl. Phys. Lett. 100, 262402 (2012); http://dx.doi.org/10.1063/1.4730960 (4 pages) | Cited 1 time

Online Publication Date: 25 June 2012

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Magnetic Schottky heterojunction fabricated from Co/p-Si is investigated. The diode showed proper rectifying property at all temperatures and evolution of a giant positive junction magnetoresistance is observed at temperatures below 50 K. Based on a simplified band structure, the spin polarization of the device is determined to be ∼31% at 10 K. A phenomenological model is proposed to explain the observed spintronic behavior of the device.
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85.30.Kk Junction diodes
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields

Field orientation dependent decorrelation of magnetization reversal in uniaxial Co-films

J. A. Arregi, O. Idigoras, P. Vavassori, and A. Berger

Appl. Phys. Lett. 100, 262403 (2012); http://dx.doi.org/10.1063/1.4730956 (4 pages) | Cited 1 time

Online Publication Date: 26 June 2012

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Magnetization reversal correlation is studied as a function of the applied field angle for thin Co-films showing in-plane uniaxial magnetocrystalline anisotropy. We find that the field orientation angle has a profound effect onto the magnetization reversal process leading to a suppression of long-range correlation at sufficiently large field angles in the presence of grain alignment disorder. Correspondingly, this behavior allows for a tuning and the local confinement of magnetization reversal even in strongly exchange-coupled films and therefore presents a most desirable scenario for ultrahigh density magnetic recording.
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75.70.Ak Magnetic properties of monolayers and thin films
75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy
75.50.Ss Magnetic recording materials
75.60.Jk Magnetization reversal mechanisms

Diffusive model of current-in-plane-tunneling in double magnetic tunnel junctions

P.-Y. Clement, C. Ducruet, C. Baraduc, M. Chshiev, and B. Diény

Appl. Phys. Lett. 100, 262404 (2012); http://dx.doi.org/10.1063/1.4730961 (4 pages)

Online Publication Date: 26 June 2012

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We propose a model that describes current-in-plane tunneling transport in double barrier magnetic tunnel junctions in diffusive regime. Our study shows that specific features appear in double junctions that are described by introducing two typical length scales. The model may be used to measure the magnetoresistance and the resistance area product of both barriers in unpatterned stacks of double barrier magnetic tunnel junctions.
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75.47.Pq Other materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
66.30.-h Diffusion in solids

Thickness dependent magnetic properties of (Ga,Mn)As ultrathin films

O. Proselkov, D. Sztenkiel, W. Stefanowicz, M. Aleszkiewicz, J. Sadowski, T. Dietl, and M. Sawicki

Appl. Phys. Lett. 100, 262405 (2012); http://dx.doi.org/10.1063/1.4731202 (4 pages) | Cited 4 times

Online Publication Date: 26 June 2012

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We report on a monotonic reduction of Curie temperature in dilute ferromagnetic semiconductor (Ga,Mn)As upon a well controlled chemical-etching/oxidizing thinning from 15 nm down to complete removal of the ferromagnetic response. The effect already starts at the very beginning of the thinning process and is accompanied by the spin reorientation transition of the in-plane uniaxial anisotropy. We postulate that a negative gradient along the growth direction of self-compensating defects (Mn interstitial) and the presence of surface donor traps gives quantitative account on these effects within the p–d mean field Zener model with adequate modifications to take a nonuniform distribution of holes and Mn cations into account.
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75.70.Ak Magnetic properties of monolayers and thin films
68.55.jd Thickness
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Pp Magnetic semiconductors
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
73.50.Fq High-field and nonlinear effects

Broadband probing magnetization dynamics of the coupled vortex state permalloy layers in nanopillars

A. A. Awad, A. Lara, V. Metlushko, K. Y. Guslienko, and F. G. Aliev

Appl. Phys. Lett. 100, 262406 (2012); http://dx.doi.org/10.1063/1.4729825 (4 pages) | Cited 2 times

Online Publication Date: 26 June 2012

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Broadband magnetization response of coupled vortex state magnetic dots in layered nanopillars was explored as a function of in-plane magnetic field and interlayer separation. For dipolarly coupled circular Py(25 nm)/Cu(20 nm)/Py(25 nm) nanopillars of 600 nm diameter, a small in-plane field splits the eigenfrequencies of azimuthal spin wave modes inducing an abrupt transition between in-phase and out-of-phase kinds of the low-lying coupled spin wave modes. The critical field for this splitting is determined by antiparallel chiralities of the vortices in the layers. Qualitatively similar (although more gradual) changes occur also in the exchange coupled Py(25 nm)/Cu(1 nm)/Py(25 nm) tri-layer nanopillars. These findings are in qualitative agreement with micromagnetic dynamic simulations.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys
75.75.-c Magnetic properties of nanostructures
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Effect of “dipolar-biasing” on the tunability of tunneling magnetoresistance in transition metal oxide systems

P. Anil Kumar and D. D. Sarma

Appl. Phys. Lett. 100, 262407 (2012); http://dx.doi.org/10.1063/1.4731206 (4 pages)

Online Publication Date: 27 June 2012

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We observe an unusual tunneling magnetoresistance (TMR) phenomenon in a composite of La2/3Sr1/3MnO3 with CoFe2O4 where the TMR versus applied magnetic field loop suggests a “negative coercive field.” Tracing its origin back to a “dipolar-biasing” of La2/3Sr1/3MnO3 by CoFe2O4, we show that the TMR of even a single composite can be tuned continuously so that the resistance peak or the highest sensitivity of the TMR can be positioned anywhere on the magnetic field axis with a suitable magnetic history of the sample. This phenomenon of an unprecedented tunability of the TMR should be present in general in all such composites.
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72.20.My Galvanomagnetic and other magnetotransport effects
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.47.-m Magnetotransport phenomena; materials for magnetotransport

Asymmetric Pt/Co/Pt-stack induced sign-control of current-induced magnetic domain-wall creep

R. Lavrijsen, P. P. J. Haazen, E. Murè, J. H. Franken, J. T. Kohlhepp, H. J. M. Swagten, and B. Koopmans

Appl. Phys. Lett. 100, 262408 (2012); http://dx.doi.org/10.1063/1.4732083 (5 pages) | Cited 2 times

Online Publication Date: 28 June 2012

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We report experimentally obtained magnetic domain wall (DW) velocities of current-assisted field-driven DW creep in perpendicularly magnetized Pt/Co/Pt. We have intentionally introduced an asymmetry in the stacks by using different thicknesses of the two Pt layers sandwiching the Co layer. Thereby, it is tested whether conflicting current-induced domain wall motion (CI-DWM) results may be intrinsically related to the basic layout and growth. We sketch a scenario which could be at the basis of contradicting reports in literature where the direction of CI-DWM conflicts with spin-torque-transfer theory, allowing the sign of the current-induced effect on DW motion to be tuned.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ch Domain walls and domain structure
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Crystalline anisotropic magnetoresistance with two-fold and eight-fold symmetry in (In,Fe)As ferromagnetic semiconductor

Pham Nam Hai, Daisuke Sasaki, Le Duc Anh, and Masaaki Tanaka

Appl. Phys. Lett. 100, 262409 (2012); http://dx.doi.org/10.1063/1.4730955 (5 pages) | Cited 2 times

Online Publication Date: 28 June 2012

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We have investigated the anisotropic magnetoresistance (AMR) of (In,Fe)As ferromagnetic semiconductor layers grown on semi-insulating GaAs substrates. In a 10 nm-thick (In,Fe)As layer which is insulating at low temperature, we observed crystalline AMR with two-fold and eight-fold symmetries. In a metallic 100 nm-thick (In,Fe)As layer with higher electron concentration, only two-fold symmetric crystalline AMR was observed. Our results demonstrate the macroscopic ferromagnetism in (In,Fe)As with magnetic anisotropy that depends on the electron concentration. Very small (∼10−5) non-crystalline AMR is also observed in the 100 nm-thick layer, suggesting that there is no s-d scattering near the Fermi level of (In,Fe)As.
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75.70.Ak Magnetic properties of monolayers and thin films
75.75.Cd Fabrication of magnetic nanostructures
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.30.Gw Magnetic anisotropy
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors

Magnetostriction in the vicinity of structural transitions in Ni2MnGa

J. M. Barandiarán, V. A. Chernenko, J. Gutiérrez, I. Orúe, and P. Lázpita

Appl. Phys. Lett. 100, 262410 (2012); http://dx.doi.org/10.1063/1.4732483 (5 pages) | Cited 2 times

Online Publication Date: 29 June 2012

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We report parallel and perpendicular magnetostriction measurements performed in polycrystalline Ni2MnGa to shed light on the magnetoelastic coupling, responsible for the ordinary magnetostriction, and giant magnetic field-induced strains (MFIS). Parallel magnetostriction is negative while its perpendicular component switches from positive to negative at the martensitic transformation. The saturation magnetostriction is negative, takes moderate values and has a large increase in absolute value at both pre- and martensitic temperatures, arising from the lattice softening at the transitions. The reported values are those of the true magnetostriction and can be a starting point for further studies of MFIS.
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75.80.+q Magnetomechanical effects, magnetostriction
81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions

Light controlled magnetoresistance and magnetic field controlled photoresistance in CoFe film deposited on BiFeO3

B. Kundys, C. Meny, M. R. J. Gibbs, V. Da Costa, M. Viret, M. Acosta, D. Colson, and B. Doudin

Appl. Phys. Lett. 100, 262411 (2012); http://dx.doi.org/10.1063/1.4731201 (4 pages)

Online Publication Date: 29 June 2012

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We present a magnetoresistive—photoresistive device based on the interaction of a piezomagnetic CoFe thin film with a photostrictive BiFeO3 (BFO) substrate that undergoes light-induced strain. The magnitude of the resistance and magnetoresistance in the CoFe film can be controlled by the wavelength of the incident light on the BiFeO3. Moreover, a light-induced decrease in anisotropic magnetoresistance is detected due to an additional magnetoelastic contribution to magnetic anisotropy of the CoFe film. This effect may find applications in photo-sensing systems, wavelength detectors and can possibly open a research development in light-controlled magnetic switching properties for next generation magnetoresistive memory devices.
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75.80.+q Magnetomechanical effects, magnetostriction
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.30.Gw Magnetic anisotropy

High propagating velocity of spin waves and temperature dependent damping in a CoFeB thin film

Haiming Yu, R. Huber, T. Schwarze, F. Brandl, T. Rapp, P. Berberich, G. Duerr, and D. Grundler

Appl. Phys. Lett. 100, 262412 (2012); http://dx.doi.org/10.1063/1.4731273 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2012

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Spin wave propagation in a magnetron-sputtered CoFeB thin film is investigated. We apply both in-plane and out-of-plane magnetic fields. At room temperature, we find velocities of up to 25 and 3.5 km/s, respectively. These values are much larger compared to a thin permalloy film. Analyzing the resonance linewidth, we obtain an intrinsic Gilbert damping parameter of about 0.007 at room temperature. It increases to 0.023 at 5 K. CoFeB is a promising material for magnonic devices supporting fast propagating spin waves.
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75.30.Ds Spin waves
75.70.Ak Magnetic properties of monolayers and thin films

Isothermal switching of perpendicular exchange bias by pulsed high magnetic field

Yu Shiratsuchi, Kohei Wakatsu, Tetsuya Nakamura, Hiroto Oikawa, Satoru Maenou, Yasuo Narumi, Kou Tazoe, Chiharu Mitsumata, Toyohiko Kinoshita, Hiroyuki Nojiri, and Ryoichi Nakatani

Appl. Phys. Lett. 100, 262413 (2012); http://dx.doi.org/10.1063/1.4731643 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2012

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Isothermal switching of a perpendicular exchange bias by a strong pulsed magnetic field has been investigated using a Pt/Co/α-Cr2O3 thin film system. The switching of the perpendicular exchange bias is accompanied by the spin reversal of interfacial uncompensated antiferromagnetic Cr spins. We have also demonstrated that the switching of the exchange bias is reversible by changing the pulsed magnetic field direction. The mechanism of the demonstrated switching is discussed from the viewpoint of the spin flop transition of the α-Cr2O3 layer.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
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