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1 Nov 2010

Volume 97, Issue 18, Articles (18xxxx)

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Appl. Phys. Lett. 97, 183105 (2010); http://dx.doi.org/10.1063/1.3506485 (3 pages)

Z. H. Zhang, X. Q. Deng, X. Q. Tan, M. Qiu, and J. B. Pan
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Nonvolatile multiple-valued memory device using lateral spin valve

T. Kimura and M. Hara

Appl. Phys. Lett. 97, 182501 (2010); http://dx.doi.org/10.1063/1.3502475 (3 pages) | Cited 2 times

Online Publication Date: 1 November 2010

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The authors propose a nonvolatile multiple-valued memory based on a nonlocal spin valve structure. Multibit informations are formed by changing the magnetization configuration in a nonlocal voltage probe consisting of a magnetic multilayer. A simple calculation method for the spin-accumulation voltage induced in lateral ferromagnetic/nonmagnetic multilayered hybrid structures is also developed on the basis of the spin resistance model. The developed model enables us to find the thickness of each ferromagnetic layer for the optimized operation of the multiple-valued memory.
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85.70.Ec Magnetostrictive, magnetoacoustic, and magnetostatic devices
85.75.Bb Magnetic memory using giant magnetoresistance
85.75.Dd Magnetic memory using magnetic tunnel junctions

Temperature dependence of spin resonance in cobalt substituted NiZnCu ferrites

A. Lucas, R. Lebourgeois, F. Mazaleyrat, and E. Labouré

Appl. Phys. Lett. 97, 182502 (2010); http://dx.doi.org/10.1063/1.3507266 (3 pages) | Cited 1 time

Online Publication Date: 2 November 2010

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Cobalt substitutions were investigated in Ni0.4Zn0.4Cu0.2Fe2O4 ferrites, initial complex permeability was then measured from 1 MHz to 1 GHz. It appears that cobalt substitution led to a decrease in the permeability and an increase in the μs×fr factor. As well, it gave to the permeability spectrum a sharp resonance character. We also observed a spin reorientation occurring at a temperature depending on the cobalt content. Study of the complex permeability versus temperature highlighted that the most resonant character was obtained at this temperature. This shows that cobalt contribution to second order magnetocrystalline anisotropy plays a leading role at this temperature.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Gg Ferrimagnetics
75.30.Gw Magnetic anisotropy

Enhanced ferromagnetic and metal insulator transition in Sm0.55Sr0.45MnO3 thin films: Role of oxygen vacancy induced quenched disorder

M. K. Srivastava, P. K. Siwach, A. Kaur, and H. K. Singh

Appl. Phys. Lett. 97, 182503 (2010); http://dx.doi.org/10.1063/1.3505327 (3 pages) | Cited 5 times

Online Publication Date: 3 November 2010

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Effect of quenched disorder (QD) caused by oxygen vacancy (OV) and substrate induced inhomogeneous compressive strain, on the magnetic and transport properties of oriented polycrystalline Sm0.55Sr0.45MnO3 thin films is investigated. QD is related intimately to the ordering/disordering of the OVs and controls the paramagnetic-ferromagnetic/insulator-metal transition. OV ordered films show enhanced TC/TIM ∼ 165 K, which is depressed by oxygen annealing. OV disordering realized by quenching reduces TC/TIM. The first order IM transition observed in SSMO single crystals is transformed into nonhysteretic and continuous one in the OV ordered films. QD appears to be diluted by OV disorder/annihilation and results in stronger carrier localization.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Ak Magnetic properties of monolayers and thin films
71.30.+h Metal-insulator transitions and other electronic transitions
72.60.+g Mixed conductivity and conductivity transitions
61.72.jd Vacancies
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Continuously graded anisotropy in single (Fe53Pt47)100−xCux films

C. L. Zha, R. K. Dumas, Y. Y. Fang, V. Bonanni, J. Nogués, and Johan Åkerman

Appl. Phys. Lett. 97, 182504 (2010); http://dx.doi.org/10.1063/1.3505521 (3 pages) | Cited 8 times

Online Publication Date: 3 November 2010

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We report on continuously graded anisotropy. During deposition, a compositional gradient is achieved by varying the Cu concentration from Cu-rich (Fe53Pt47)70Cu30 to Cu-free Fe53Pt47. The anisotropy gradient is then realized after annealing using the composition dependence of the low-anisotropy (A1) to high-anisotropy (L10) ordering temperature. The critical role of the annealing temperature on the resultant anisotropy gradient is investigated. Magnetic measurements support the creation of an anisotropy gradient in properly annealed films which exhibit both a reduced coercivity and moderate thermal stability. These results demonstrate that an anisotropy gradient can be realized, and tailored, in single continuous films without the need for multilayers.
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75.30.Gw Magnetic anisotropy
81.40.Gh Other heat and thermomechanical treatments
75.70.Ak Magnetic properties of monolayers and thin films
68.55.at Other materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Observation of tunable exchange bias in Sr2YbRuO6

R. P. Singh, C. V. Tomy, and A. K. Grover

Appl. Phys. Lett. 97, 182505 (2010); http://dx.doi.org/10.1063/1.3505525 (3 pages) | Cited 4 times

Online Publication Date: 3 November 2010

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The double perovskite compound, Sr2YbRuO6, displays reversal in the orientation of magnetic moments along with negative magnetization due to an underlying magnetic compensation phenomenon. The exchange bias (EB) field below the compensation temperature could be the usual negative or the positive depending on the initial cooling field. This EB attribute has the potential of getting tuned in a preselected manner, as the positive EB field is seen to crossover from positive to negative value above Tcomp.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.70.Pq Ruthenates
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ee Antiferromagnetics
75.30.Cr Saturation moments and magnetic susceptibilities

Current-induced resonant depinning of a transverse magnetic domain wall in a spin valve nanostrip

P. J. Metaxas, A. Anane, V. Cros, J. Grollier, C. Deranlot, Y. Lemaître, S. Xavier, C. Ulysse, G. Faini, F. Petroff, and A. Fert

Appl. Phys. Lett. 97, 182506 (2010); http://dx.doi.org/10.1063/1.3507895 (3 pages)

Online Publication Date: 4 November 2010

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We study the impact of rf and dc currents on domain wall depinning in the soft layer of a 120 nm wide Co/Cu/NiFe spin valve nanostrip. A strong resonant reduction in the depinning field (from ∼ 75 to 25 Oe) is observed for rf currents near 3.5 GHz. Notably, the features of the resonant depinning depend not only on the rf current but also on the simultaneously applied dc current. Consequently, we discuss both the role of the adiabatic spin torque at resonance and that of the current generated Oersted fields.
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75.60.Ch Domain walls and domain structure
75.47.-m Magnetotransport phenomena; materials for magnetotransport
75.75.-c Magnetic properties of nanostructures

Amplitude and phase noise of magnetic tunnel junction oscillators

M. Quinsat, D. Gusakova, J. F. Sierra, J. P. Michel, D. Houssameddine, B. Delaet, M.-C. Cyrille, U. Ebels, B. Dieny, L. D. Buda-Prejbeanu, J. A. Katine, D. Mauri, A. Zeltser, M. Prigent, J.-C. Nallatamby, et al.

Appl. Phys. Lett. 97, 182507 (2010); http://dx.doi.org/10.1063/1.3506901 (3 pages) | Cited 5 times

Online Publication Date: 5 November 2010

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The microwave emission linewidth of spin transfer torque nano-oscillators is closely related to their phase and amplitude noise that can be extracted from the magnetoresistive voltage signal V(t) using single shot time domain techniques. Here we report on phase and amplitude noise studies for MgO based magnetic tunnel junction oscillators. The analysis of the power spectral densities allows one to separate the linear and nonlinear contributions to the phase noise, the nonlinear contribution being due to the coupling between phase and amplitude. The coupling strength as well as the amplitude relaxation rate can be directly extracted.
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84.30.Ng Oscillators, pulse generators, and function generators
84.40.-x Radiowave and microwave (including millimeter wave) technology
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Exchange-coupling of c-axis oriented L10–FePd and Fe in FePd/Fe thin films

T. Ichitsubo, S. Takashima, E. Matsubara, Y. Tamada, and T. Ono

Appl. Phys. Lett. 97, 182508 (2010); http://dx.doi.org/10.1063/1.3514582 (3 pages) | Cited 2 times

Online Publication Date: 5 November 2010

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This letter reports the control of the c-axis orientation and the magnetic properties of L10 FePd in the well-annealed FePd/Fe thin films Fe(20 nm)/FePd(10 nm)/Fe(5 nm)/SiO2-substrate and Fe(20 nm)/FePd(5 nm)/Fe(5 nm)/SiO2-substrate, with the compositions of dual phase region in phase equilibrium. After annealing at 550 °C for 24 h, the c-axis of L10 FePd is controlled to be oriented in the normal direction in the soft Fe matrix. These thin films exhibit the exchange-coupling of hard FePd with soft Fe, and a characteristic spring-magnet behavior showed up reversibly as a significant jump from positive to negative in the magnetization reversal.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys
75.30.Et Exchange and superexchange interactions
75.60.Nt Magnetic annealing and temperature-hysteresis effects
81.40.Gh Other heat and thermomechanical treatments
75.60.Jk Magnetization reversal mechanisms

Competition of the antiferromagnetic superexchange with the ferromagnetic double exchange in dicobalt complexes

Lin He and Lin Guo

Appl. Phys. Lett. 97, 182509 (2010); http://dx.doi.org/10.1063/1.3514583 (3 pages) | Cited 2 times

Online Publication Date: 5 November 2010

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Here we report the competition of superexchange and double exchange interactions in the molecule [(NH3)4Co(OH)2Co(NH3)4]4+. Magnetic data reveal a S = 3 ground state arising from the competition. The canting angle between the magnetic moments of the Co2+ and Co4+ ions is about 92.5°. The double exchange parameter is estimated to be sevenfold of the superexchange parameter. The result presented here opens a way to introducing of ferromagnetic double exchange interaction to the single molecular magnets via the charge disproportionation between valence-variable transition-metal ions.
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75.30.Et Exchange and superexchange interactions
75.50.Ee Antiferromagnetics
75.50.Xx Molecular magnets
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Cr Saturation moments and magnetic susceptibilities
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