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11 Feb 2013

Volume 102, Issue 6, Articles (06xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 102, 063701 (2013); http://dx.doi.org/10.1063/1.4790115 (5 pages)

In-Tsang Lin, Hong-Chang Yang, and Jyh-Horng Chen
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Thermally driven asymmetric responses of grains versus spin-glass related distributions of blocking temperature in exchange biased Co/IrMn bilayers

V. Baltz

Appl. Phys. Lett. 102, 062410 (2013); http://dx.doi.org/10.1063/1.4792347 (4 pages)

Online Publication Date: 13 February 2013

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Controlling ferromagnetic/antiferromagnetic blocking temperatures in exchange biased based devices appears crucial for applications. The blocking temperature is ascribed to the ability of both antiferromagnetic grains and interfacial spin-glass-like phases to withstand ferromagnetic magnetization reversal. To better understand the respective contributions of grains versus spin-glass, blocking temperature distributions were measured after various thermal treatments for cobalt/iridium-manganese bilayers. The high-temperature contribution linked to antiferromagnetic grains shifts towards lower temperatures above a threshold thermal annealing. In contrast, the occurrence and evolution of training effects for the low-temperature contribution only agree with its inferred interfacial spin-glass-like origin.
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81.05.Bx Metals, semimetals, and alloys
75.30.Et Exchange and superexchange interactions
75.50.Cc Other ferromagnetic metals and alloys
75.50.Ee Antiferromagnetics
75.50.Lk Spin glasses and other random magnets
75.60.Jk Magnetization reversal mechanisms

Can cation vacancy defects induce room temperature ferromagnetism in GaN?

Xiaopeng Wang, Mingwen Zhao, Tao He, Zhenhai Wang, and Xiangdong Liu

Appl. Phys. Lett. 102, 062411 (2013); http://dx.doi.org/10.1063/1.4792528 (4 pages)

Online Publication Date: 13 February 2013

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The unique properties of gallium nitride (GaN) crystal, such as a wide band-gap and high thermal conductivity, make it ideal material for electronic and optoelectronic devices. Achieving room temperature (RT) ferromagnetism in GaN becomes crucial. In previous works, gallium vacancy (VGa) was expected to be promising for reaching this goal. However, using an accurate hybrid exchange-correlation functional, we show that the largest value of J0 is only 3.3 meV at the VGa density of 1.28 × 1021 cm−3, corresponding to a Curie temperature of 150 K. This suggests that VGa cannot induce RT ferromagnetism at the density lower than that value.
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61.72.jd Vacancies
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Cc Other ferromagnetic metals and alloys
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors

Transport of perpendicular spin in a semiconductor channel via a fully electrical method

Joohyung Bae, Kyung-Ho Kim, Jung-Min Han, Hyun Cheol Koo, Byoung-Chul Min, Hyung-jun Kim, Joonyeon Chang, Suk Hee Han, and Sang Ho Lim

Appl. Phys. Lett. 102, 062412 (2013); http://dx.doi.org/10.1063/1.4792690 (4 pages)

Online Publication Date: 13 February 2013

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The transport of perpendicular spins in a GaAs channel is investigated via a fully electrical method. A Tb20Fe62Co18/Co40Fe40B20/MgO contact is used to inject perpendicular spin into the GaAs channel, where the Tb20Fe62Co18 layer produces perpendicular magnetization and the Co40Fe40B20 layer enhances the spin polarization of the injection current. By measuring the three-terminal Hanle effect with an in-plane field, we obtained a spin signal of 0.65 Ω (0.04 Ω) and a spin lifetime of 0.30 ns (0.17 ns) at 1.8 K (300 K). The observed spin signal with a MgO barrier is more than double of that without a MgO barrier.
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81.05.Ea III-V semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.80.Ey III-V and II-VI semiconductors
72.25.Dc Spin polarized transport in semiconductors
78.20.Ls Magneto-optical effects

Anomalous Hall effect and magnetoresistance behavior in Co/Pd1−xAgx multilayers

Z. B. Guo, W. B. Mi, A. Manchon, J. Q. Li, B. Zhang, P. G. Barba, and X. X. Zhang

Appl. Phys. Lett. 102, 062413 (2013); http://dx.doi.org/10.1063/1.4792054 (4 pages)

Online Publication Date: 13 February 2013

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In this paper, we report anomalous Hall effect (AHE) correlated with the magnetoresistance behavior in [Co/Pd1−xAgx]n multilayers. For the multilayers with n = 6, the increase in Ag content from x = 0 to 0.52 induces the change in AHE sign from negative surface scattering-dominated AHE to positive interface scattering-dominated AHE, which is accompanied with the transition from anisotropy magnetoresistance (AMR) dominated transport to giant magnetoresistance (GMR) dominated transport. For n = 80, scaling analysis with Rs∝ρxxγ yields γ ∼ 3.44 for x = 0.52 which presents GMR-type transport, in contrast to γ ∼ 5.7 for x = 0 which presents AMR-type transport.
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75.47.De Giant magnetoresistance
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.25.+i Surface conductivity and carrier phenomena
75.30.Gw Magnetic anisotropy

Impact of reduced dimensionality on the magnetic and magnetocaloric response of La0.7Ca0.3MnO3

P. Lampen, N. S. Bingham, M. H. Phan, H. Kim, M. Osofsky, A. Piqué, T. L. Phan, S. C. Yu, and H. Srikanth

Appl. Phys. Lett. 102, 062414 (2013); http://dx.doi.org/10.1063/1.4792239 (5 pages) | Cited 1 time

Online Publication Date: 13 February 2013

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Understanding the impact of reduced dimensionality on the magnetic and magnetocaloric responses of a material is vital in incorporating it as an active magnetic refrigerant in cooling devices. By contrasting the magnetic and magnetocaloric behaviors of bulk polycrystalline, sol-gel derived nanocrystalline, and pulsed laser deposited thin film forms of the La0.7Ca0.3MnO3 system, we show that reducing the dimensionality of a ferromagnetic material tends to broaden and shift the paramagnetic to ferromagnetic transition to lower temperatures, while decreasing the saturation magnetization and the magnitude of the magnetic entropy change. Relative to its bulk counterpart, a pronounced broadening of the magnetic entropy change peak in the thin film leads to enhanced refrigerant capacity—an important figure-of-merit for active magnetic refrigeration technology. With reduced dimensionality, universal curves based on re-scaled entropy change curves tend toward collapse, indicating a weakening of the first order nature of the transition in the nanocrystalline samples and a crossover to second order in the thin film.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Tt Fine-particle systems; nanocrystalline materials
75.75.-c Magnetic properties of nanostructures
81.15.Fg Pulsed laser ablation deposition
68.55.at Other materials
81.16.Mk Laser-assisted deposition

Uniaxial anisotropy of two-magnon scattering in an ultrathin epitaxial Fe layer on GaAs

H. Kurebayashi, T. D. Skinner, K. Khazen, K. Olejník, D. Fang, C. Ciccarelli, R. P. Campion, B. L. Gallagher, L. Fleet, A. Hirohata, and A. J. Ferguson

Appl. Phys. Lett. 102, 062415 (2013); http://dx.doi.org/10.1063/1.4792269 (5 pages)

Online Publication Date: 13 February 2013

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We report an on-chip, electrically detected ferromagnetic resonance study on microbars made from GaAs/Fe(1 nm)/GaAs layers. Our experiments, performed at several different microwave frequencies and static magnetic field directions, enable us to observe a strong in-plane uniaxial anisotropy of the linewidth. We attribute the linewidth anisotropy to the two magnon scattering process, supporting this by calculations of possible linewidth broadening mechanisms. Our findings are useful for designing future high-performance spintronic devices based on nanoscale magnetic structures.
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75.30.Gw Magnetic anisotropy
75.50.Bb Fe and its alloys
75.70.Ak Magnetic properties of monolayers and thin films
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
68.55.A- Nucleation and growth
75.30.Ds Spin waves

Systematic study of magnetotransport properties and enhanced low-field magnetoresistance in thin films of La0.67Sr0.33MnO3 + Mg(O)

M. Staruch, C. Cantoni, and M. Jain

Appl. Phys. Lett. 102, 062416 (2013); http://dx.doi.org/10.1063/1.4792688 (5 pages)

Online Publication Date: 14 February 2013

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La, Sr, Mn, and Mg precursors were mixed in stoichiometric ratio 0.67/0.33/1/x with solvent and were spin-coated onto (001) LaAlO3 substrates. X-ray diffraction and elemental mapping of these films indicate that for small addition of Mg precursor, Mg2+ acts as a dopant in La0.67Sr0.33MnO3 phase and for higher concentrations, MgO phase separates out. Curie temperature and metal-insulator transition temperature systematically decrease with increasing molar concentration of Mg(O). Low-field magnetoresistance of films significantly enhanced by Mg addition and for the highest amount of Mg at 10 K, values were −35.5% and −83.2% with 0.5 T and 3 T applied fields, respectively.
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75.47.Gk Colossal magnetoresistance
75.47.Lx Magnetic oxides
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
71.30.+h Metal-insulator transitions and other electronic transitions
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials

Heat-induced damping modification in yttrium iron garnet/platinum hetero-structures

M. B. Jungfleisch, T. An, K. Ando, Y. Kajiwara, K. Uchida, V. I. Vasyuchka, A. V. Chumak, A. A. Serga, E. Saitoh, and B. Hillebrands

Appl. Phys. Lett. 102, 062417 (2013); http://dx.doi.org/10.1063/1.4792701 (4 pages) | Cited 1 time

Online Publication Date: 15 February 2013

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We experimentally demonstrate the manipulation of magnetization relaxation utilizing a temperature difference across the thickness of an yttrium iron garnet/platinum hetero-structure: the damping is either increased or decreased depending on the sign of the temperature gradient. This effect might be explained by a thermally induced spin torque on the magnetization precession. The heat-induced variation of the damping is detected by microwave techniques as well as by a DC voltage caused by spin pumping into the adjacent Pt layer and the subsequent conversion into a charge current by the inverse spin Hall effect.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.40.Ns Metal-nonmetal contacts
75.50.Gg Ferrimagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.25.Mk Spin transport through interfaces
72.20.My Galvanomagnetic and other magnetotransport effects

Influence of a Dy overlayer on the precessional dynamics of a ferromagnetic thin film

M. K. Marcham, W. Yu, P. S. Keatley, L. R. Shelford, P. Shafer, S. A. Cavill, H. Qing, A. Neudert, J. R. Childress, J. A. Katine, E. Arenholz, N. D. Telling, G. van der Laan, and R. J. Hicken

Appl. Phys. Lett. 102, 062418 (2013); http://dx.doi.org/10.1063/1.4792740 (4 pages)

Online Publication Date: 15 February 2013

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Precessional dynamics of a Co50Fe50(0.7)/Ni90Fe10(5)/Dy(1)/Ru(3) (thicknesses in nm) thin film have been explored by low temperature time-resolved magneto-optical Kerr effect and phase-resolved x-ray ferromagnetic resonance measurements. As the temperature was decreased from 300 to 140 K, the magnetic damping was found to increase rapidly while the resonance field was strongly reduced. Static x-ray magnetic circular dichroism measurements revealed increasing ferromagnetic order of the Dy moment antiparallel to that of Co50Fe50/Ni90Fe10. Increased coupling of the Dy orbital moment to the precessing spin magnetization leads to significantly increased damping and gyromagnetic ratio of the film while leaving its magnetic anisotropy effectively unchanged.
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75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.50.Bb Fe and its alloys
75.70.Ak Magnetic properties of monolayers and thin films
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
78.20.Ls Magneto-optical effects
75.30.Gw Magnetic anisotropy

Tunable all electric spin polarizer

J. Charles, N. Bhandari, J. Wan, M. Cahay, and R. S. Newrock

Appl. Phys. Lett. 102, 062419 (2013); http://dx.doi.org/10.1063/1.4792745 (3 pages)

Online Publication Date: 15 February 2013

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We propose a tunable all-electric spin polarizer made of a quantum point contact (QPC) with four gates—two in-plane side gates in series. The pair of gates near the source is asymmetrically biased to create spin polarization in the QPC channel, the second pair near the drain is symmetrically biased and this bias is varied to maximize the QPC spin polarization. The range of common mode bias on the first set of gates over which maximum spin polarization is achieved is much broader for the four gate structure compared to a QPC with a single pair of gates.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
85.35.-p Nanoelectronic devices

Highly (001)-oriented thin continuous L10 FePt film by introducing an FeOx cap layer

Jung-Wei Liao, Kuo-Feng Huang, Liang-Wei Wang, Wu-Chang Tsai, Wei-Chih Wen, Chao-Chien Chiang, Hong-Ji Lin, Fan-Hsiu Chang, and Chih-Huang Lai

Appl. Phys. Lett. 102, 062420 (2013); http://dx.doi.org/10.1063/1.4793189 (5 pages) | Cited 1 time

Online Publication Date: 15 February 2013

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We demonstrate a thin and continuous L10 FePt film with a well-aligned (001) texture directly grown on Si || SiO2 substrates by introducing an FeOx cap layer. The agglomeration of capped FePt films is greatly suppressed by inhibiting the surface diffusion. This, in turn, yields a continuous and smooth film, which significantly promotes the (001) out-of-plane orientation and perpendicular anisotropy. The reduction of Fe oxides occurs during annealing, which not only promotes interdiffusion of Fe and Pt for L10 ordering but also removes the cap layer simultaneously. Therefore, additional etching for the cap layer is not required for further fabricating bit patterned media.
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81.05.Bx Metals, semimetals, and alloys
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
75.30.Gw Magnetic anisotropy
75.70.Ak Magnetic properties of monolayers and thin films
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Low-loss tunable metamaterials using superconducting circuits with Josephson junctions

P. Jung, S. Butz, S. V. Shitov, and A. V. Ustinov

Appl. Phys. Lett. 102, 062601 (2013); http://dx.doi.org/10.1063/1.4792705 (4 pages)

Online Publication Date: 14 February 2013

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We report on experiments with superconducting metamaterials containing Josephson junctions. In these structures, split-ring resonators used in conventional metamaterials are replaced by superconducting loops that are interrupted by Josephson junctions, so called rf-SQUIDs. Like the split-ring resonators, these elements can be seen as LC-resonators that couple to the magnetic field. The advantage of superconducting thin-film metamaterials is that, due to the tunable intrinsic inductance of the Josephson junction, the resonance frequency of the rf-SQUID can be changed by applying an external dc magnetic field. We present experimental results that demonstrate the tunability of the resonance frequency of these devices.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.50.+r Tunneling phenomena; Josephson effects
74.78.-w Superconducting films and low-dimensional structures
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The possibility of giant dielectric materials for multilayer ceramic capacitors

Tatsuya Ishii, Makoto Endo, Kenichiro Masuda, and Keisuke Ishida

Appl. Phys. Lett. 102, 062901 (2013); http://dx.doi.org/10.1063/1.4791555 (4 pages)

Online Publication Date: 11 February 2013

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There have been numerous reports on discovery of giant dielectric permittivity materials called internal barrier layer capacitor in the recent years. We took particular note of one of such materials, i.e., BaTiO3 with SiO2 coating. It shows expressions of giant electric permittivity when processed by spark plasma sintering. So we evaluated various electrical characteristics of this material to find out whether it is applicable to multilayer ceramic capacitors. Our evaluation revealed that the isolated surface structure is the sole cause of expressions of giant dielectric permittivity.
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84.32.Tt Capacitors
77.22.Ch Permittivity (dielectric function)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Origin of large recoverable strain in 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 near the ferroelectric-relaxor transition

Hugh Simons, John E. Daniels, Julia Glaum, Andrew J. Studer, Jacob L. Jones, and Mark Hoffman

Appl. Phys. Lett. 102, 062902 (2013); http://dx.doi.org/10.1063/1.4790285 (5 pages)

Online Publication Date: 11 February 2013

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Piezoceramics of composition 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 demonstrate large recoverable strain at elevated temperature (T > 75 °C), which is absent at room temperature. In situ neutron diffraction was used to measure changes in the crystallographic and domain structures during electric field application at temperatures ranging from 25 °C to 100 °C. Quantitative evaluation of the ferroelastic domain volume fraction in the field-induced phases enabled calculation of the strain contribution from non-180° domain switching. The large recoverable strain is shown to be associated with the reversible nature of the phase transformation. These findings have implications to additional BNT-xBT-based composition and other relaxor ferroelectrics.
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77.80.B- Phase transitions and Curie point
77.65.-j Piezoelectricity and electromechanical effects
77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.fg Shape-memory effect; yield stress; superelasticity

The multiferroic perovskite YFeO3

Mingyu Shang, Chenyang Zhang, Tingsong Zhang, Lin Yuan, Lei Ge, Hongming Yuan, and Shouhua Feng

Appl. Phys. Lett. 102, 062903 (2013); http://dx.doi.org/10.1063/1.4791697 (3 pages)

Online Publication Date: 12 February 2013

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The orthoferrite YFeO3 with orthorhombic perovskite structure (Pnma) has been synthesized by mild hydrothermal method. The temperature-dependent magnetization and hysteresis loops indicate that, due to the superexchange and Dzyaloshinskii-Moriya interactions in the crystals, the Fe spins order antiferromagnetically at the Néel temperature 655 K with a weak ferromagnetic moment. The observation of saturation polarization loops at room temperature and 77 K provide evidence for the ferroelectric character of the polycrystalline samples. Its Curie temperature has been obtained from the temperature dependence of the relative permittivities and thermal analysis. As a result, the structure exhibits simultaneously weak ferromagnetic and ferroelectric behavior.
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77.80.B- Phase transitions and Curie point
75.30.Et Exchange and superexchange interactions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Gg Ferrimagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.85.+t Magnetoelectric effects, multiferroics

Negative dielectric constant manifested by static electricity

Han Yan, Cindy Zhao, Kevin Wang, Lucy Deng, Matthew Ma, and Gu Xu

Appl. Phys. Lett. 102, 062904 (2013); http://dx.doi.org/10.1063/1.4792064 (4 pages)

Online Publication Date: 12 February 2013

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Negative dielectric constant has long been pursued for a possible revolution in electronics and photonics. It is usually found in systems containing free electrons under high frequency oscillating field, but not involving static charges or insulating materials. Here, we report the observation of the phenomenon in an insulating polymer containing static electricity, which lasts for several weeks, where negative capacitance persists from <1 Hz up to MHz frequency, also presenting an unusual spiral curve in impedance spectrum, producing inductors without bulky magnetic coils.
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77.22.Ch Permittivity (dielectric function)
72.30.+q High-frequency effects; plasma effects

Multilevel resistive switching memory with amorphous InGaZnO-based thin film

Ching-Hui Hsu, Yang-Shun Fan, and Po-Tsun Liu

Appl. Phys. Lett. 102, 062905 (2013); http://dx.doi.org/10.1063/1.4792316 (3 pages)

Online Publication Date: 13 February 2013

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Multi-level storage capability of resistive random access memory (RRAM) using amorphous indium-gallium-zinc-oxide (InGaZnO) thin film is demonstrated by the TiN/Ti/InGaZnO/Pt device structure under different operation modes. The distinct four-level resistance states can be obtained by varying either the trigger voltage pulse or the compliance current. In addition, the RRAM devices exhibit superior characteristics of programming/erasing endurance and data retention for the application of multi-level nonvolatile memory technology. Physical transport mechanisms for the multi-level resistive switching characteristics are also deduced in this study.
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84.30.Sk Pulse and digital circuits

Estimation of intrinsic contribution to dielectric response of Pb0.92La0.08Zr0.52Ti0.48O3 thin films at low frequencies using high bias fields

Manoj Narayanan, Sheng Tong, Shanshan Liu, Beihai Ma, and Uthamalingam Balachandran

Appl. Phys. Lett. 102, 062906 (2013); http://dx.doi.org/10.1063/1.4792529 (4 pages)

Online Publication Date: 13 February 2013

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Because most domain wall motion (extrinsic) is arrested at high bias fields, experiments were conducted to evaluate the lattice (intrinsic) contributions to the dielectric response of lead lanthanum zirconate titanate (PLZT) at 0-100 MV/m, 213-523 K, and 1-1000 kHz. The intrinsic contribution depended weakly on bias field and frequency, while the extrinsic contribution strongly depended on these same parameters as well as temperature. The threshold bias field required to suppress domain wall motion in PLZT thin films was ∼20-25 MV/m, and the intrinsic permittivity measured at those fields was ∼300-350, in agreement with literature values.
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77.22.Ch Permittivity (dielectric function)
77.65.-j Piezoelectricity and electromechanical effects
77.80.Dj Domain structure; hysteresis
77.84.Cg PZT ceramics and other titanates
77.55.hj PZT

Electronic band alignment and electron transport in Cr/BaTiO3/Pt ferroelectric tunnel junctions

A. Zenkevich, M. Minnekaev, Yu. Matveyev, Yu. Lebedinskii, K. Bulakh, A. Chouprik, A. Baturin, K. Maksimova, S. Thiess, and W. Drube

Appl. Phys. Lett. 102, 062907 (2013); http://dx.doi.org/10.1063/1.4792525 (5 pages) | Cited 1 time

Online Publication Date: 14 February 2013

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Electroresistance in ferroelectric tunnel junctions is controlled by changes in the electrostatic potential profile across the junction upon polarization reversal of the ultrathin ferroelectric barrier layer. Here, hard X-ray photoemission spectroscopy is used to reconstruct the electric potential barrier profile in as-grown Cr/BaTiO3(001)/Pt(001) heterostructures. Transport properties of Cr/BaTiO3/Pt junctions with a sub-μm Cr top electrode are interpreted in terms of tunneling electroresistance with resistance changes of a factor of ∼30 upon polarization reversal. By fitting the I-V characteristics with the model employing an experimentally determined electric potential barrier we derive the step height changes at the BaTiO3/Pt (Cr/BaTiO3) interface +0.42(−0.03) eV following downward to upward polarization reversal.
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73.40.Rw Metal-insulator-metal structures
79.60.Jv Interfaces; heterostructures; nanostructures
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
73.20.At Surface states, band structure, electron density of states

Effects of holmium substitution on multiferroic properties in Tb0.67Ho0.33MnO3

M. Staruch, G. Lawes, A. Kumarasiri, L. F. Cotica, and M. Jain

Appl. Phys. Lett. 102, 062908 (2013); http://dx.doi.org/10.1063/1.4792526 (5 pages)

Online Publication Date: 14 February 2013

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In this work, the structural, electrical, and magnetic properties of orthorhombic TbMnO3 and Tb0.67Ho0.33MnO3 ceramics are presented. The lattice parameters and the Mn-O-Mn bond angle were found to decrease with Ho-substitution as evidenced by Rietveld refinement of the X-ray diffraction data and Raman spectroscopy measurements. A weak ferromagnetic moment was observed in both dc and ac magnetic measurements of the Ho-substituted sample possibly due to spin canting in the antiferromagnetic phase. Tb0.67Ho0.33MnO3 was confirmed to be multiferroic with appearance of spontaneous polarization below 25 K and an additional increase in polarization ∼15.5 K associated with the ordering of the Ho3+ moments.
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75.85.+t Magnetoelectric effects, multiferroics
61.66.Fn Inorganic compounds
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Ee Antiferromagnetics
77.22.Ej Polarization and depolarization

Enhancement of resonant and non-resonant magnetoelectric coupling in multiferroic laminates with anisotropic piezoelectric properties

Deepak Rajaram Patil, Yisheng Chai, Rahul C. Kambale, Byung-Gu Jeon, Kyongjun Yoo, Jungho Ryu, Woon-Ha Yoon, Dong-Soo Park, Dae-Yong Jeong, Sang-Goo Lee, Jeongho Lee, Joong-Hee Nam, Jeong-Ho Cho, Byung-Ik Kim, and Kee Hoon Kim

Appl. Phys. Lett. 102, 062909 (2013); http://dx.doi.org/10.1063/1.4792590 (4 pages)

Online Publication Date: 15 February 2013

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Giant transverse magnetoelectric voltage coefficients |mathE| = 751 and 305 V/cmOe at two electromechanical antiresonance frequencies are found in the symmetric metglas/[011]-oriented 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 crystal/metglas laminate. Unique torsional and diagonal vibration modes are identified to be responsible for those giant |mathE| values. Moreover, mathE is found to be anisotropic depending on the in-plane magnetic field directions, making the piezoelectrics with anisotropic planar piezoelectricity potentially useful base materials for multi-frequency, phase-sensitive magnetoelectric devices.
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75.85.+t Magnetoelectric effects, multiferroics
77.84.Cg PZT ceramics and other titanates
77.65.Fs Electromechanical resonance; quartz resonators
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Terahertz emission from GaAs-AlGaAs core-shell nanowires on Si (100) substrate: Effects of applied magnetic field and excitation wavelength

Jasher John Ibanes, Ma. Herminia Balgos, Rafael Jaculbia, Arnel Salvador, Armando Somintac, Elmer Estacio, Christopher T. Que, Satoshi Tsuzuki, Kohji Yamamoto, and Masahiko Tani

Appl. Phys. Lett. 102, 063101 (2013); http://dx.doi.org/10.1063/1.4791570 (3 pages)

Online Publication Date: 11 February 2013

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Terahertz (THz) emission from GaAs-AlGaAs core-shell nanowires (CSNW) on silicon (100) substrates was investigated using THz time-domain spectroscopy. The applied magnetic field polarity dependence strongly suggests that THz emission originated from photo-carriers in the CSNWs. Optical excitation of the GaAs-AlGaAs core-shell yielded a wider THz emission bandwidth compared with that of just the GaAs core material. This result is currently attributed to faster carrier lifetimes in the AlGaAs shell. The THz emission spectral data are supported by time-resolved photoluminescence studies.
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78.55.Cr III-V semiconductors
78.67.Uh Nanowires
61.46.-w Structure of nanoscale materials
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Intrinsic spin noise in MgO magnetic tunnel junctions

F. Delgado, K. Lopez, R. Ferreira, and J. Fernández-Rossier

Appl. Phys. Lett. 102, 063102 (2013); http://dx.doi.org/10.1063/1.4791594 (4 pages)

Online Publication Date: 11 February 2013

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We consider two intrinsic sources of noise in ultra-sensitive magnetic field sensors based on MgO magnetic tunnel junctions, coming both from 25Mg nuclear spins (I = 5/2, 10% natural abundance) and S = 1 Mg-vacancies. While nuclear spins induce noise peaked in the MHz frequency range, the vacancies noise peaks in the GHz range. We find that the nuclear noise in submicron devices has a similar magnitude than the 1/f noise, while the vacancy-induced noise dominates in the GHz range. Interestingly, the noise spectrum under a finite magnetic field gradient may provide spatial information about the spins in the MgO layer.
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07.55.-w Magnetic instruments and components
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
85.75.Ss Magnetic field sensors using spin polarized transport

P(VDF-TrFE-CFE) terpolymer thin-film for high performance nonvolatile memory

Xin Chen, Lu Liu, Shi-Zheng Liu, Yu-Shuang Cui, Xiang-Zhong Chen, Hai-Xiong Ge, and Qun-Dong Shen

Appl. Phys. Lett. 102, 063103 (2013); http://dx.doi.org/10.1063/1.4791598 (4 pages) | Cited 1 time

Online Publication Date: 11 February 2013

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Vinylidene fluoride-trifluoroethylene-chlorofluoroethylene terpolymer, P(VDF-TrFE-CFE), with small amount of CFE is utilized for thin-film nonvolatile memory. Polarization switching voltage for a 50 nm-thick film can be as low as 1 V, and is well suited for integrated driving electronics. The writing-erasing procedure is completely reversible. High signal-to-noise and high capability for data storage are observed in this memory system. Polarization state of the terpolymer is rather stable, making it applicable for memory devices. Polarization switching behavior in the terpolymer can be ascribed to reduced polar domain size with respect to the P(VDF-TrFE) copolymer, and energy cost of domain wall motion during electrically polarization switching decreases.
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68.55.-a Thin film structure and morphology
84.30.Sk Pulse and digital circuits

Bi doping modulating structure and phase-change properties of GeTe nanowires

Jie Zhang, Rong Huang, Lin Shi, Long Wang, Fenfen Wei, Tao Kong, and Guosheng Cheng

Appl. Phys. Lett. 102, 063104 (2013); http://dx.doi.org/10.1063/1.4790590 (4 pages)

Online Publication Date: 11 February 2013

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Bi-doped GeTe nanowires were fabricated using chemical vapor deposition. Composition and microstructure characterizations indicated that Bi (∼3 at. %) doping preserved GeTe rhombohedral structure with slight X-ray diffraction peak shifts, implying material parameters variation. A doping model was proposed where three Bi atoms replaced the middle adjacent Ge sites of (001) plane, accompanied by two adjacent Ge vacancies right over Bi atoms. Ab initio calculations re-validated cell parameters change. Furthermore, Bi-doping process resulted in crystalline and amorphous state resistances increased by ∼2 orders, while a crystallization time dramatically reduced down to 50 μs, 20 times shorter compared to undoped nanowires.
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64.70.Nd Structural transitions in nanoscale materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
61.72.up Other materials
81.07.Gf Nanowires
61.43.Dq Amorphous semiconductors, metals, and alloys
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