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23 Jul 2012

Volume 101, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 043101 (2012); http://dx.doi.org/10.1063/1.4737152 (4 pages)

Toshiaki Tanigaki, Yoshikatsu Inada, Shinji Aizawa, Takahiro Suzuki, Hyun Soon Park, Tsuyoshi Matsuda, Akira Taniyama, Daisuke Shindo, and Akira Tonomura
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Enhanced magnetic and dielectric properties of Eu and Co co-doped BiFeO3 nanoparticles

Kaushik Chakrabarti, Kajari Das, Babusona Sarkar, Sirshendu Ghosh, S. K. De, Godhuli Sinha, and J. Lahtinen

Appl. Phys. Lett. 101, 042401 (2012); http://dx.doi.org/10.1063/1.4738992 (5 pages) | Cited 8 times

Online Publication Date: 23 July 2012

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Bi1−xEuxFe1−yCoyO3 (x = 0, 0.01; y = 0, 0.01) nanoparticles, having an average size of 13 nm, were prepared by a simple sol gel route. Strong electronegativity of Eu3+ and smaller oxidation-reduction potential of Co3+/Co2+ (0.55 eV) than Fe3+/Fe2+ (1.3 eV) increase the concentration of Fe3+ ions with doping. Distinct magnetic hysteresis and complete saturation of magnetisation indicate the presence of ferromagnetic phase. The successful co-doping of Eu and Co into BiFeO3 (BFO) lattice dramatically enhances the saturation magnetization (Ms) and coercivity (Hc) by about 20 times than that of pure BiFeO3. A large value of dielectric constant of about 650, low loss (<0.001), and small leakage current density (1.79 × 10−8 A/cm2) are observed for the co-doped sample.
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75.75.Cd Fabrication of magnetic nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
81.16.-c Methods of micro- and nanofabrication and processing

Magnetoelastic resonance sensor for remote strain measurements

Thomas Huber, Bernhard Bergmair, Christoph Vogler, Florian Bruckner, Gino Hrkac, and Dieter Suess

Appl. Phys. Lett. 101, 042402 (2012); http://dx.doi.org/10.1063/1.4735340 (3 pages)

Online Publication Date: 23 July 2012

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A low cost passive wireless strain sensor is proposed. The basis of the sensor is formed by two softmagnetic magnetostrictive ribbons. The first magnetostrictive ribbon transforms mechanical stress into a stress dependent magnetic field. The second ribbon senses this field by magnetoacoustic oscillations. The resonance frequency directly depends on the applied mechanical stress. For the proposed sensor, a gauge factor Gf, which is defined as the relative change of the resonance frequency divided by the strain ɛ, of Gf = 380 is obtained. This is significantly higher than the gauge factor of standard metal foil strain gages.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Pz Instruments for strain, force, and torque
75.80.+q Magnetomechanical effects, magnetostriction
85.70.Ec Magnetostrictive, magnetoacoustic, and magnetostatic devices

Interface induced inverse spin Hall effect in bismuth/permalloy bilayer

Dazhi Hou, Z. Qiu, K. Harii, Y. Kajiwara, K. Uchida, Y. Fujikawa, H. Nakayama, T. Yoshino, T. An, K. Ando, Xiaofeng Jin, and E. Saitoh

Appl. Phys. Lett. 101, 042403 (2012); http://dx.doi.org/10.1063/1.4738786 (4 pages) | Cited 1 time

Online Publication Date: 24 July 2012

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Inverse spin Hall effect has been investigated in bismuth(Bi)/permalloy(Py) bilayer films by using the spin pumping at room temperature. From the ferromagnetic-resonance-spectrum linewidth data, Bi is proved to be a good spin sink in our structure. We measured inverse spin Hall voltage and conductance of the Bi/Py bilayer and found that the inverse spin Hall current, Ic, decreases with increasing the Bi thickness, which is in contrast to the former understanding in similar bilayer systems, e.g., Pt/Py. We constructed a model to explain the thickness dependence of Ic quantitatively, in which spin transport modulation near Bi/Py interface is considered.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
72.20.My Galvanomagnetic and other magnetotransport effects
72.25.Mk Spin transport through interfaces
75.50.Bb Fe and its alloys
75.70.Ak Magnetic properties of monolayers and thin films

Huge Goos-Hänchen effect for spin waves: A promising tool for study magnetic properties at interfaces

Yu. S. Dadoenkova, N. N. Dadoenkova, I. L. Lyubchanskii, M. L. Sokolovskyy, J. W. Kłos, J. Romero-Vivas, and M. Krawczyk

Appl. Phys. Lett. 101, 042404 (2012); http://dx.doi.org/10.1063/1.4738987 (5 pages)

Online Publication Date: 24 July 2012

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A possibility to observe huge lateral shift (Goos-Hänchen effect) of exchange spin wave reflected from the interface of two ferromagnetic materials is theoretically investigated. The strong dependence of this effect on the exchange coupling between two magnetic media as well as on the magnetic field is obtained. We show that nonzero interlayer exchange is necessary to observe the lateral shift of reflected spin-wave, and this shift can reach values up to a few hundreds of wavelengths. The observed effect can be a useful tool in investigation of the magnetic coupling between two magnetic materials also through nonmagnetic spacer.
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75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Interfacial current-induced torques in Pt/Co/GdOx

Satoru Emori, David C. Bono, and Geoffrey S. D. Beach

Appl. Phys. Lett. 101, 042405 (2012); http://dx.doi.org/10.1063/1.4737899 (4 pages) | Cited 1 time

Online Publication Date: 24 July 2012

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Current-driven domain wall (DW) motion is investigated in Pt/Co/GdOx nanostrips with perpendicular magnetic anisotropy. Measurements of the propagation field and the energy barrier for thermally activated DW motion reveal a large current-induced torque equivalent to an out-of-plane magnetic field of ∼60 Oe per 1011 A/m2. This same field-to-current scaling is shown to hold in both the slow thermally activated and fast near-flow regimes of DW motion. The current-induced torque decreases with 4 Å of Pt decorating the Co/GdOx interface and vanishes entirely with Pt replacing GdOx, suggesting that the Co/GdOx interface contributes directly to highly efficient current-driven DW motion.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.Fk Domain structures in nanoparticles
75.30.Gw Magnetic anisotropy
75.60.Ch Domain walls and domain structure

Evidence of oxygen-vacancy-induced ferromagnetic order in single crystal Mn-doped SrTiO3

Srimanta Middey, Carlo Meneghini, and Sugata Ray

Appl. Phys. Lett. 101, 042406 (2012); http://dx.doi.org/10.1063/1.4738785 (4 pages) | Cited 1 time

Online Publication Date: 25 July 2012

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The appearance of ferromagnetic order in the presence of oxygen vacancies has been investigated in dilute Mn-doped SrTiO3 single crystals. The sample without vacancy is paraelectric and paramagnetic down to low temperature. However, incorporation of vacancy makes the system metallic and clear ferromagnetic hysteresis loop is observed at low temperature. X-ray diffraction, x-ray absorption near edge spectroscopy measurement do not reveal any signature of secondary magnetic phase. Diffuse reflectivity measurement negates the bound magnetic polaron model for ferromagnetism in the reduced system and thus spontaneous magnetism suggests the possibility of a carrier-mediated Ruderman-Kittel-Kasuya-Yosida mechanism.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.70.Dm X-ray absorption spectra
61.72.jd Vacancies
71.70.Gm Exchange interactions
75.50.Dd Nonmetallic ferromagnetic materials

Biaxial strain effect of spin dependent tunneling in MgO magnetic tunnel junctions

Ajeesh M. Sahadevan, Ravi K. Tiwari, Gopinadhan Kalon, Charanjit S. Bhatia, Mark Saeys, and Hyunsoo Yang

Appl. Phys. Lett. 101, 042407 (2012); http://dx.doi.org/10.1063/1.4738787 (5 pages) | Cited 1 time

Online Publication Date: 25 July 2012

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We study the effect of strain on magnetic tunnel junctions induced by a diamond like carbon (DLC) film. The junction resistance as well as the tunnel magnetoresistance (TMR) reduces with the DLC film. Non-equilibrium Green’s function quantum transport calculations show that the application of biaxial strain increases the conductance for both the parallel and anti-parallel configurations. However, the conductance for the minority channel and for the anti-parallel configuration is significantly more sensitive to strain, which drastically increases transmission through a MgO tunnel barrier, therefore, the TMR ratio decreases with biaxial strain.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Spectroscopic defect imaging in magnetic nanostructure arrays

Han-Jong Chia, Feng Guo, L. M. Belova, and R. D. McMichael

Appl. Phys. Lett. 101, 042408 (2012); http://dx.doi.org/10.1063/1.4738789 (4 pages) | Cited 1 time

Online Publication Date: 25 July 2012

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We introduce a method for imaging defective structures in an array of magnetic nanodevices using ferromagnetic resonance force microscopy with contrast between normal and defective devices provided through differences in resonance condition. In a demonstration of this technique, two dimensional scans of an array resolve not only intentional differences in resonant field between 200 nm circular dots and an intentional oval “defect,” but also smaller differences between the nominally identical circular dots in the array.
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85.70.-w Magnetic devices
07.79.Pk Magnetic force microscopes

Nanomagnetism of cobalt ferrite-based spin filters probed by spin-polarized tunneling

Sylvia Matzen, Jean-Baptiste Moussy, Richard Mattana, Karim Bouzehouane, Cyrile Deranlot, and Frédéric Petroff

Appl. Phys. Lett. 101, 042409 (2012); http://dx.doi.org/10.1063/1.4738790 (4 pages) | Cited 1 time

Online Publication Date: 25 July 2012

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The magnetism of ferrite ultrathin films has been probed at nanoscale by spin-polarized tunneling transport in CoFe2O4-based room-temperature spin filters. By significantly reducing the Pt/CoFe2O4/Al2O3/Co junctions’ size (cross sections ∼5 nm) in comparison with usual microjunctions, transport through a ferrite single magnetic domain has been achieved. Our tunnel magnetoresistance measurements at the nanoscale have revealed very well defined resistance states and the generation of the highest spin filtering efficiency (−8%) at room temperature. A uniaxial magnetic anisotropy has been evidenced in CoFe2O4, showing that these magnetotransport measurements offer a unique probe of a single magnetic domain in ferrite ultrathin films.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
FREE

Spin waves turning a corner

K. Vogt, H. Schultheiss, S. Jain, J. E. Pearson, A. Hoffmann, S. D. Bader, and B. Hillebrands

Appl. Phys. Lett. 101, 042410 (2012); http://dx.doi.org/10.1063/1.4738887 (3 pages) | Cited 4 times

Online Publication Date: 25 July 2012

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We studied the propagation of spin waves in a Ni81Fe19 micro-waveguide comprising a smooth, S-shaped bend using Brillouin light scattering microscopy. A direct current flowing through a gold wire underneath the Ni81Fe19 provides a local magnetic field, which maintains a transverse magnetization around the bend of the waveguide. It is demonstrated that spin-wave propagation inside the bend can be realized in contrast to the case of an externally applied magnetic field, which generates strong inhomogeneities in the internal effective field distribution, preventing any spin-wave propagation across the bend.
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75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)

Influence of rare earth moment ordering on magnetic entropy change in Nd0.5Sr0.5CoO3

Pawan Kumar and R. Mahendiran

Appl. Phys. Lett. 101, 042411 (2012); http://dx.doi.org/10.1063/1.4738889 (5 pages) | Cited 2 times

Online Publication Date: 25 July 2012

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Field-cooled magnetization of Nd0.5Sr0.5CoO3 shows an anomalous maximum at T* = 76 K ≪ TC = 228 K, where TC is the ferromagnetic Curie temperature of the Co-sublattice. While T* shows a systematic shift with increasing magnetic field(H), the maximum does not disappear even at H = 7 T. We suggest that Nd(4f) moment is polarized by the molecular field of Co sublattice and order antiparallel to the Co(3d) spin lattice below T*, which causes magnetic entropy to decrease (increase) with increasing H for T > T* (T below T*). Critical exponents associated with the ferromagnetic phase transition were analyzed and found to be close to the mean-field model values.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Dd Nonmetallic ferromagnetic materials

Wireless and passive temperature indicator utilizing the large hysteresis of magnetic shape memory alloys

Bernhard Bergmair, Jian Liu, Thomas Huber, Oliver Gutfleisch, and Dieter Suess

Appl. Phys. Lett. 101, 042412 (2012); http://dx.doi.org/10.1063/1.4739836 (4 pages)

Online Publication Date: 26 July 2012

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An ultra-low cost, wireless magnetoelastic temperature indicator is presented. It comprises a magnetostrictive amorphous ribbon, a Ni-Mn-Sn-Co magnetic shape memory alloy with a highly tunable transformation temperature, and a bias magnet. It allows to remotely detect irreversible changes due to transgressions of upper or lower temperature thresholds. Therefore, the proposed temperature indicator is particularly suitable for monitoring the temperature-controlled supply chain of, e.g., deep frozen and chilled food or pharmaceuticals.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.80.+q Magnetomechanical effects, magnetostriction
75.50.Kj Amorphous and quasicrystalline magnetic materials

Remarkable current-enhanced photoconductivity in oxygen-deficient La7/8Sr1/8MnO3−δ thin film

L. Hu, Z. G. Sheng, Y. N. Huang, W. H. Song, and Y. P. Sun

Appl. Phys. Lett. 101, 042413 (2012); http://dx.doi.org/10.1063/1.4739842 (4 pages) | Cited 1 time

Online Publication Date: 26 July 2012

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Effects of light and electrical current on the electrical transport properties of oxygen-deficient La7/8Sr1/8MnO3−δ thin films have been investigated. The light illumination causes a resistance drop to show photoconductivity effect. Moreover, the photoconductivity can be remarkably enhanced by increasing the electrical current, that is, it exhibits current-enhanced photoconductivity (CEPC) effect. The CEPC ratio achieves 80% at 300 K with light intensity of 56.7 mW cm−2 and electrical current of 20 μA. The phenomena are explained by a photoinduced localized insulator-metal transition and stabilization of conducting paths by the electrical current. These results may be important for practical applications in photoelectric devices.
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73.50.Pz Photoconduction and photovoltaic effects
73.61.Ng Insulators
71.30.+h Metal-insulator transitions and other electronic transitions
72.40.+w Photoconduction and photovoltaic effects

Half metallic character of NiMoO3 driven by the electron correlation and spin-orbit coupling

J. Wang and Z. J. Wu

Appl. Phys. Lett. 101, 042414 (2012); http://dx.doi.org/10.1063/1.4739847 (4 pages)

Online Publication Date: 26 July 2012

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The semiconducting behavior of NiCrO3 is driven by the strong electron correlation of transition metal 3d electrons. By substituting Cr with more itinerant 4d transition metal Mo, NiMoO3 is designed and studied by the first principles. It is isostructural and isovalent to NiCrO3. Compensated half metal is obtained when considering electron correlation alone. Inclusion both spin-orbit coupling and electron correlation induce a large orbital moment on Ni (−0.23 μB) due to the Coulomb enhanced spin-orbit coupling. This makes NiMoO3 a half metallic ferrimagnet with nonintegral magnetic moment. The orbital moment of Mo is negligible. Pressure destroys the half metallic character.
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71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Gg Ferrimagnetics
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
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