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3 Aug 2009

Volume 95, Issue 5, Articles (05xxxx)

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Appl. Phys. Lett. 95, 052901 (2009); http://dx.doi.org/10.1063/1.3190518 (3 pages)

Didit Yudistira, Sarah Benchabane, Davide Janner, and Valerio Pruneri
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Magnetoelectric effect at the SrRuO3/BaTiO3 (001) interface: An ab initio study

Manish K. Niranjan, J. D. Burton, J. P. Velev, S. S. Jaswal, and E. Y. Tsymbal

Appl. Phys. Lett. 95, 052501 (2009); http://dx.doi.org/10.1063/1.3193679 (3 pages) | Cited 26 times

Online Publication Date: 3 August 2009

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Ferromagnet/ferroelectric interface materials have emerged as structures with strong magnetoelectric coupling that may exist due to unconventional physical mechanisms. Here we present a first-principles study of the magnetoelectric effect at the ferromagnet/ferroelectric SrRuO3/BaTiO3 (001) interface. We find that the exchange splitting of the spin-polarized band structure, and therefore the magnetization, at the interface can be altered substantially by reversal of the ferroelectric polarization in the BaTiO3. These magnetoelectric effects originate from the screening of polarization charges at the SrRuO3/BaTiO3 interface and are consistent with the Stoner model for itinerant magnetism.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
72.25.Mk Spin transport through interfaces
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.10.Lp Band and itinerant models
77.22.Ej Polarization and depolarization

Photovoltaic effect in the La0.67Ca0.33MnO3/LaMnO3/SrTiO3:Nb heterojunctions with variant LaMnO3 layers

A. D. Wei, J. R. Sun, W. M. Lü, and B. G. Shen

Appl. Phys. Lett. 95, 052502 (2009); http://dx.doi.org/10.1063/1.3194776 (3 pages) | Cited 4 times

Online Publication Date: 3 August 2009

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Influence of LaMnO3 layer, 0–12 nm in thickness, on photovoltaic effect (PVE) has been experimentally studied for the La0.67Ca0.33MnO3/LaMnO3/SrTiO3:Nb junction. Presence of LaMnO3 causes an obvious weakening of the PVE, demonstrated by the reduction in the carrier density excited by each photon. The interfacial barrier deduced from the PVE shows a rapid growth, from ∼ 1.22 to ∼ 1.45 eV, as the layer thickness increases from 0 to 2 nm, and saturates at ∼ 1.5 eV above 2 nm. On the contrary, current-voltage characteristics suggest a smooth reduction in interfacial barrier with layer thickness. These results can be quantitatively understood assuming the occurrence of a notch and a spike in the conduction band edges at the interface of the junction.
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73.50.Pz Photoconduction and photovoltaic effects
73.40.-c Electronic transport in interface structures
73.20.At Surface states, band structure, electron density of states
73.61.Ng Insulators

Periodicity in Al/Ti superconducting single electron transistors

Sarah J. MacLeod, Sergey Kafanov, and Jukka P. Pekola

Appl. Phys. Lett. 95, 052503 (2009); http://dx.doi.org/10.1063/1.3194777 (3 pages)

Online Publication Date: 3 August 2009

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We present experiments on single Cooper-pair transistors made of two different superconducting materials. We chose Ti and Al to create an energy gap profile such that the island has a higher gap than the leads, thereby acting as a barrier to quasiparticle tunneling. Our transport measurements demonstrate that quasiparticle poisoning is suppressed in all our TiAlTi structures (higher gap for the island) with clear 2e periodicity observed, whereas full quasiparticle poisoning is observed in all AlTiAl devices (higher gap for the leads) with e periodicity.
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85.35.Gv Single electron devices
74.70.-b Superconducting materials other than cuprates
71.20.-b Electron density of states and band structure of crystalline solids

Enhanced superconducting transition temperature in FeSe0.5Te0.5 thin films

Weidong Si, Zhi-Wei Lin, Qing Jie, Wei-Guo Yin, Juan Zhou, Genda Gu, P. D. Johnson, and Qiang Li

Appl. Phys. Lett. 95, 052504 (2009); http://dx.doi.org/10.1063/1.3195076 (3 pages) | Cited 35 times

Online Publication Date: 3 August 2009

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We report magnetoresistive and structural measurements of superconducting FeSe0.5Te0.5 epitaxial thin films grown by pulsed laser deposition. Enhanced onset superconducting transition temperature ( ∼ 17 K) is observed in some of these films. Structural analysis by x-ray diffraction and high resolution transmission electron microscopy reveal that these films generally have significantly shorter out-of-plane lattice constant c than the bulk value, suggesting that the out-of-plane changes have a dominating impact on the superconducting transition in iron-based superconductors. Our data also indicate that the upper critical field Hc2(0) of those films may reach as high as 50 T.
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74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.78.-w Superconducting films and low-dimensional structures
74.25.Ha Magnetic properties including vortex structures and related phenomena
81.15.Fg Pulsed laser ablation deposition
61.66.Fn Inorganic compounds

A superconducting transistorlike device having good input-output isolation.

I. P. Nevirkovets

Appl. Phys. Lett. 95, 052505 (2009); http://dx.doi.org/10.1063/1.3189283 (3 pages) | Cited 2 times

Online Publication Date: 3 August 2009

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A multiterminal superconducting device with the S1IS2FIS3 structure (where S, I, and F denote a superconductor, an insulator, and a ferromagnetic material) is fabricated and characterized. Introducing a thin ferromagnetic layer into the middle electrode dramatically reduces parasitic back action of the acceptor junction (S1IS2) bias current on the injector junction (S2FIS3) current-voltage characteristic as compared with that for the formerly reported quiteron, a device exploiting similar operation principle.
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85.25.Cp Josephson devices

Temperature dependence of resistance in epitaxial Fe/MgO/Fe magnetic tunnel junctions

Q. L. Ma, S. G. Wang, J. Zhang, Yan Wang, R. C. C. Ward, C. Wang, A. Kohn, X.-G. Zhang, and X. F. Han

Appl. Phys. Lett. 95, 052506 (2009); http://dx.doi.org/10.1063/1.3194150 (3 pages) | Cited 11 times

Online Publication Date: 4 August 2009

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The temperature dependence of resistance in parallel (P) and antiparallel (AP) configurations (RP,AP) has been investigated in epitaxial Fe/MgO/Fe junctions with varying MgO barrier thicknesses tMgO. RAP exhibits a substantial decrease with increasing temperature for samples with tMgO ranging from 3.0 to 1.5 nm. In contrast, RP is approximately temperature independent when tMgO = 3.0 nm and increases with temperature when tMgO = 2.1 and 1.5 nm. Possible origins of this temperature dependence of resistance, which include taking into account a spin independent term and consideration of spin-flip scattering, are discussed. We attribute the temperature dependence of RP,AP to the misalignment of magnetic moments in the electrodes due to thermal excitations and its effect on the spin dependent tunneling.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.Pq Other materials

Dynamic dipolar interaction effect on spin-transfer switching with perpendicular anisotropy

Yongcheng Qiu, Zongzhi Zhang, Q. Y. Jin, and Yaowen Liu

Appl. Phys. Lett. 95, 052507 (2009); http://dx.doi.org/10.1063/1.3197590 (3 pages) | Cited 1 time

Online Publication Date: 5 August 2009

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Micromagnetic simulation is employed to study the influence of neighboring cells on spin torque switching in a matrix of nanopillars with perpendicular magnetic anisotropy. We find that with the decreased separation the critical switching current densities can be strongly modified for different matrix configurations as compared to an isolated disk element. Such variations are attributed to the stray fields rather than the resonant effect, although both of them arise from the dipolar interaction between the target and neighboring cells. The Bloch wall mediated switching process is evidenced by the magnetization snapshots, which agrees with the recent experimental results.
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75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.30.Gw Magnetic anisotropy
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.60.Jk Magnetization reversal mechanisms

A charge-passivated codoping approach for enhancing ferromagnetism and electron transport on rutile TiO2(110) surface

Qinghua Liu, Jingfu He, Cong Mai, Tao Yao, Zhiyun Pan, Zhihu Sun, Wensheng Yan, Ziyu Wu, and Shiqiang Wei

Appl. Phys. Lett. 95, 052508 (2009); http://dx.doi.org/10.1063/1.3194300 (3 pages) | Cited 2 times

Online Publication Date: 5 August 2009

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We performed a first-principles study on the magnetism and electronic character of rutile Fe:TiO2(110) mediated by oxygen vacancies (OVs) and codopant. The results show the magnetic interaction between Fe ions is a ferromagnetic (FM) superexchange nature, while the presence of OV makes it turn to an antiferromagnetic behavior. It is found when the system is codoped with oppositely charged P, the interactions are rehabilitated to FM coupling. The electronic structure analysis reveals that this is principally attributed to the sp-d hybridizations between P and Fe, which finally activate a long-ranged FM interaction between the Fe ions, and substantially facilitate the electron transport.
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75.30.Et Exchange and superexchange interactions
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
75.50.Ee Antiferromagnetics
61.72.U- Doping and impurity implantation
71.20.Ps Other inorganic compounds
74.62.Dh Effects of crystal defects, doping and substitution

Ferromagnetic resonance and damping in granular Co–Cr films with perpendicular anisotropy

Pavol Krivosik, Sangita S. Kalarickal, Nan Mo, Stella Wu, and Carl E. Patton

Appl. Phys. Lett. 95, 052509 (2009); http://dx.doi.org/10.1063/1.3200238 (3 pages) | Cited 4 times

Online Publication Date: 6 August 2009

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The 17.3 GHz ferromagnetic resonance field (HFMR) and linewidth (ΔH) have been measured as a function of the angle (θH) between the external magnetic field and film normal for a 16 nm thick Co–Cr granular film with uniaxial perpendicular anisotropy. The HFMR(θH) response is significantly different from the uniform rotation prediction. The ΔH(θH) dependence shows major deviations from the Gilbert phenomenological damping model. Both dependences can be modeled simultaneously through a combination of two-magnon scattering processes, inhomogeneity line broadening, and an intrinsic damping from magnon-electron scattering processes, with a Gilbert damping α-value of 0.004.
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75.70.Ak Magnetic properties of monolayers and thin films
75.30.Gw Magnetic anisotropy
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.50.Cc Other ferromagnetic metals and alloys

Excellent low field magnetoresistance properties of the La0.7Sr0.3Mn1+dO3-manganese oxide composites

Young-Min Kang, Hyo-Jin Kim, and Sang-Im Yoo

Appl. Phys. Lett. 95, 052510 (2009); http://dx.doi.org/10.1063/1.3177192 (3 pages) | Cited 14 times

Online Publication Date: 6 August 2009

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Excellent low field magnetoresistance (LFMR) properties could be achieved from the La0.7Sr0.3Mn1+dO3 (LSMO)-manganese oxide polycrystalline composites. While the improvement of LFMR properties in the perovskite maganite-oxide composites is commonly accompanied with a significant increase in their electrical resistivities, optimally processed LSMO-manganese composite in this study exhibits greatly enhanced LFMR of 1.7% at 0.5 kOe and unprecedentedly high maximum dMR/dH value of 28.3% kOe−1 at 300 K without an appreciable increase in its resistivity, which is attributable to the formation of sharp grain boundaries between neighboring LSMO ferromagnetic grains, acting as very effective spin-dependent scattering center.
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72.20.My Galvanomagnetic and other magnetotransport effects
61.72.Mm Grain and twin boundaries
72.80.Sk Insulators
75.50.Dd Nonmetallic ferromagnetic materials

Revisiting magnetization processes in granular hard magnetic materials

A. N. Dobrynin, V. M. T. S. Barthem, and D. Givord

Appl. Phys. Lett. 95, 052511 (2009); http://dx.doi.org/10.1063/1.3193543 (3 pages) | Cited 13 times

Online Publication Date: 7 August 2009

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We show that the generally accepted demagnetizing field corrections are not applicable to the broad class of modern granular magnetic materials, where magnetization reversal occurs via discrete switching of the moments of individual grains, and thus the self-demagnetizing field of a given grain is proportional to the spontaneous magnetization Ms, not to the sample magnetization M. This leads to the fact that the self-demagnetizing field must be considered as a contribution to the coercive field and that the slope of the magnetization variation is higher than the classical demagnetizing field slope. This description of demagnetization processes is confirmed by numerical modeling.
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75.60.Jk Magnetization reversal mechanisms
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.05.Rm Porous materials; granular materials
75.50.Ww Permanent magnets
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