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25 Jul 2011

Volume 99, Issue 4, Articles (04xxxx)

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Appl. Phys. Lett. 99, 041102 (2011); http://dx.doi.org/10.1063/1.3615051 (3 pages)

M. Davanço, M. T. Rakher, D. Schuh, A. Badolato, and K. Srinivasan
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Junction size effect on switching current and thermal stability in CoFeB/MgO perpendicular magnetic tunnel junctions

H. Sato, M. Yamanouchi, K. Miura, S. Ikeda, H. D. Gan, K. Mizunuma, R. Koizumi, F. Matsukura, and H. Ohno

Appl. Phys. Lett. 99, 042501 (2011); http://dx.doi.org/10.1063/1.3617429 (3 pages) | Cited 13 times

Online Publication Date: 26 July 2011

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Junction size dependence of critical current (IC0) for spin transfer torque switching and thermal stability factor (E/kBT) was examined in CoFeB/MgO perpendicular magnetic tunnel junctions (p-MTJs). The IC0 increased with increasing recording layer area (Srec). On the other hand, the E/kBT showed almost constant values even though the Srec was increased from ∼1500 nm2 (44 nmφ) to ∼5000 nm2 (76 nmφ). Both IC0 and E/kBT behavior can be explained with assuming that the nucleation type magnetization reversal takes place in CoFeB/MgO p-MTJs.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
64.60.Q- Nucleation
75.60.Jk Magnetization reversal mechanisms

Temperature dependent coercivity crossover in pseudo-spin-valve magnetic tunnel junctions with perpendicular anisotropy

G. Feng, H. C. Wu, J. F. Feng, and J. M. D. Coey

Appl. Phys. Lett. 99, 042502 (2011); http://dx.doi.org/10.1063/1.3614000 (3 pages) | Cited 7 times

Online Publication Date: 26 July 2011

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We report the temperature dependent collapse of tunnel magnetoresistance (TMR) in perpendicular anisotropy magnetic tunnel junctions (pMTJs) with AlOx barriers and (Co/Pt)3 multilayer electrodes, due to the coercivity crossover of the top and bottom (Co/Pt)3 stacks. The different temperature dependence of two (Co/Pt)3 stacks in pMTJs is mainly caused by the additional perpendicular anisotropy created at interface between the ferromagnetic electrode and the AlOx barrier.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Gw Magnetic anisotropy
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Vv High coercivity materials

Evolution of magnetic bubble domains in manganite films

S. R. Bakaul, W. Lin, and T. Wu

Appl. Phys. Lett. 99, 042503 (2011); http://dx.doi.org/10.1063/1.3615708 (3 pages) | Cited 10 times

Online Publication Date: 26 July 2011

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We report a thickness-dependent evolution of magnetic domains from long stripe-like to bubble-like entities in La1−xSrxMnO3 (x ∼ 0.3) (LSMO) films grown on LaAlO3 substrates. By using 2-D fast Fourier transformation of magnetic force microscopy images and power spectral density function, we accurately determine the domain width in LSMO films with a wide range of thickness (50–325 nm). We find that the domain size scales with the Kittel’s square root law [C. Kittel, Phys. Rev. 70, 965 (1946).] only when reduced film thicknesses are used, which suggests the critical role of substrate-film interaction in domain formation.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.70.Ak Magnetic properties of monolayers and thin films

Robust room temperature ferromagnetism in Cu doped ZnO thin films

Zaheer Ahmed Khan and Subhasis Ghosh

Appl. Phys. Lett. 99, 042504 (2011); http://dx.doi.org/10.1063/1.3615714 (3 pages) | Cited 12 times

Online Publication Date: 26 July 2011

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We report the growth of high quality Cu doped ZnO thin films by magnetron sputtering. High level of Cu doping has been achieved at higher growth temperature. Room temperature ferromagnetism, with magnetic moment initially increasing and then decreasing with Cu content, has been observed in the thin film without post growth annealing. Observed ferromagnetism is robust and does not disappear upon annealing.
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81.05.Dz II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
68.55.ag Semiconductors
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films

Quasi-one-dimensional miniature multiferroic magnetic field sensor with high sensitivity at zero bias field

Yajie Chen, Scott M. Gillette, Trifon Fitchorov, Liping Jiang, Hongbo Hao, Jiheng Li, Xuexu Gao, Anton Geiler, C. Vittoria, and V. G. Harris

Appl. Phys. Lett. 99, 042505 (2011); http://dx.doi.org/10.1063/1.3617434 (3 pages) | Cited 9 times

Online Publication Date: 28 July 2011

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A miniature, quasi one dimensional, magnetic field sensor based on magnetoelectric coupling is presented. The magnetoelectric sensor makes use of the d31 coupling mode between a piezoelectric lead zirconate titanate tube and FeNi magnetostrictive wire. The sensors demonstrate high sensitivity, high signal-to-noise ratio, and low noise floor at zero DC magnetic bias field and at low frequency resulting in smaller, lower power consumption, and volumetric efficiency. Experiments indicate a zero bias field sensitivity of 16.5 mV/Oe at 100 Hz stemming from a magnetoelectric coefficient of 1.65 V/cm-Oe. The results are quantitatively described by a theoretical model of laminate composites.
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85.75.Ss Magnetic field sensors using spin polarized transport
07.55.-w Magnetic instruments and components

Signal transfer in a chain of stray-field coupled ferromagnetic squares

Andreas Vogel, Michael Martens, Markus Weigand, and Guido Meier

Appl. Phys. Lett. 99, 042506 (2011); http://dx.doi.org/10.1063/1.3614551 (3 pages) | Cited 5 times

Online Publication Date: 29 July 2011

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We study the vortex-core dynamics in a chain of three stray-field coupled permalloy squares. Time-resolved scanning transmission x-ray microscopy is employed to image the out-of-plane magnetization of the cores. After exciting the first element via a short in-plane magnetic field pulse, the excitation can be transferred through the chain via dipolar interaction. The transfer efficiency of the gyrotropic vortex motion strongly depends on the configuration of the core polarizations. For alternating polarizations, a transfer efficiency of about 56% to the third square is achieved. The chain can be switched back and forth between the transmitting and a locking state.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys

Growth and properties of heavy fermion CeCu2Ge2 and CeFe2Ge2 thin films

Yize Stephanie Li, Mao Zheng, Brian Mulcahy, Laura H. Greene, and James N. Eckstein

Appl. Phys. Lett. 99, 042507 (2011); http://dx.doi.org/10.1063/1.3610975 (3 pages) | Cited 2 times

Online Publication Date: 29 July 2011

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Epitaxial films of heavy fermion CeCu2Ge2 and CeFe2Ge2 are grown on DyScO3 and MgO substrates using molecular beam epitaxy. The growth begins via island nucleation leading to a granular morphology. The grains grow flat with c-axis orientation after nucleating, as indicated by in-situ reflection high energy electron diffraction (RHEED) and ex-situ analysis including atomic force microscopy (AFM) and x-ray diffraction (XRD). These single phase films show similar temperature dependent transport to single crystals of the materials indicating that similar collective order occurs in the films as in single crystals.
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68.55.at Other materials
71.27.+a Strongly correlated electron systems; heavy fermions
81.05.Bx Metals, semimetals, and alloys
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
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