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17 Jun 2013

Volume 102, Issue 24 (partial)

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Hybrid microcavity humidity sensor

Simin Mehrabani, Philip Kwong, Malancha Gupta, and Andrea M. Armani

Appl. Phys. Lett. 102, 241101 (2013); http://dx.doi.org/10.1063/1.4811265 (4 pages)

Online Publication Date: 17 June 2013

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This work presents an optical humidity sensing technique based on the combination of a whispering gallery mode microtoroidal cavity sensor and a nm-scale thick humidity-responsive polymer coating deposited via the initiated chemical vapor deposition process. As a result of the conformational change by the polymer in response to humidity, the sensitivity is increased by nearly two orders of magnitude in comparison to conventional refractometric sensing. Additionally, the dependence of the device performance on the film thickness is studied. Specifically, the thinner film enabled a faster response rate, yet a slower recovery rate, as compared to the thicker films.
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07.07.Vx Hygrometers; hygrometry
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Radiative cooling by light down conversion of InGaN light emitting diode bonded to a Si wafer

V. K. Malyutenko, V. V. Bogatyrenko, and O. Yu. Malyutenko

Appl. Phys. Lett. 102, 241102 (2013); http://dx.doi.org/10.1063/1.4811373 (3 pages)

Online Publication Date: 17 June 2013

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Using the recently proposed process of radiative cooling by light down conversion, we demonstrate cooling of about 5 K for InGaN light emitting diode (39 mg thermal load) that is self-heated up to 450 K and bonded to a cooler, a 15 × 15 × 4 mm3 Si wafer pumped with an above bandgap excitation from a 1.09-μm diode laser. Cooling occurs due to the enhancement of thermal emission in an initially transparent Si wafer when the overall energy of multiple (about 20) below bandgap photons escaping the wafer exceeds the energy of the single pumped photon. The cooling efficiency amounts to 93%.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.60.Jb Light-emitting devices

The origins of polarimetric image contrast between healthy and cancerous human colon tissue

T. Novikova, A. Pierangelo, S. Manhas, A. Benali, P. Validire, B. Gayet, and A. De Martino

Appl. Phys. Lett. 102, 241103 (2013); http://dx.doi.org/10.1063/1.4811414 (4 pages)

Online Publication Date: 17 June 2013

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Experimentally measured spectral Mueller matrix images of ex vivo human colon tissue revealed the contrast enhancement between healthy and cancerous zones of colon specimen compared to unpolarized intensity images. Cancer development starts with abnormal changes which being not yet visible macroscopically may alter the polarization of reflected light. We have shown with experiments and modeling that light scattering by small (sub wavelength) scatterers and light absorption (mainly due to blood hemoglobin) are the key factors for observed polarimetric image contrast. These findings can pave the way for the alternative optical technique for the monitoring and early detection of cancer.
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87.57.cj Contrast
87.63.lm Image enhancement
87.19.xj Cancer

High field terahertz pulse generation from plasma wakefield driven by tailored laser pulses

Zi-Yu Chen

Appl. Phys. Lett. 102, 241104 (2013); http://dx.doi.org/10.1063/1.4811552 (5 pages)

Online Publication Date: 17 June 2013

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A scheme to generate high field terahertz (THz) pulses by using tailored laser pulses interaction with a gas target is proposed. The laser wakefield based THz source is emitted from the asymmetric laser shape induced plasma transverse transient net currents. Particle-in-cell simulations show that THz emission with electric filed strength over 1 GV/cm can be obtained with incident laser at 1×1019 W/cm2 level, and the corresponding energy conversion efficiency is more than 10−4. The intensity scaling holds up to high field strengths. Such a source also has a broad tunability range in amplitude, frequency spectra, and temporal shape.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.65.Rr Particle-in-cell method
52.50.Dg Plasma sources
52.25.Fi Transport properties
52.38.-r Laser-plasma interactions

Strong luminescence induced by elastic deformation of piezoelectric crystals

V. K. Chandra, B. P. Chandra, and Piyush Jha

Appl. Phys. Lett. 102, 241105 (2013); http://dx.doi.org/10.1063/1.4811160 (4 pages)

Online Publication Date: 17 June 2013

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The luminescence induced by elastic deformation of solids, called the phenomenon of elastico-mechanoluminescence (EML), is observed in several materials. For applied pressure in the range of 17 MPa, certain crystals emit intense EML, which can be seen in day light with naked eye. In the present paper, we explore that, as the piezoelectric constant near the photo-generated electric dipoles formed by trapping of charge carriers in crystals is several times higher as compared to that at normal sites, the piezoelectrically induced detrapping of charge carriers and EML emission may take place for less value of the pressure applied onto the crystals.
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78.60.Mq Sonoluminescence, triboluminescence
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
62.20.F- Deformation and plasticity
77.65.Bn Piezoelectric and electrostrictive constants

Electric-field-tunable defect mode in one-dimensional photonic crystal operating in the terahertz range

V. Skoromets, H. Němec, C. Kadlec, D. Fattakhova-Rohlfing, and P. Kužel

Appl. Phys. Lett. 102, 241106 (2013); http://dx.doi.org/10.1063/1.4809821 (4 pages)

Online Publication Date: 18 June 2013

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A one-dimensional photonic crystal possessing an electric-field-tunable defect mode in the lowest forbidden band is demonstrated. The compact photonic structure consists of two symmetric Bragg mirrors made of alternate quarter-wave layers of SiO2 and CeO2 separated by a defect layer of an incipient ferroelectric SrTiO3 with electrodes transparent for terahertz radiation on its both sides. The applied bias is then perpendicular to the layer and modifies the in-plane dielectric function, which is probed by the transverse terahertz wave. The observed tunable behavior is in agreement with the model of the ferroelectric soft mode behavior in SrTiO3 single crystals. The defect-mode frequency tunability is proportional to that of the soft mode: we achieved a relative tunability of 6.5% at 105 K under an electric bias of 60 kV/cm.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
42.70.Qs Photonic bandgap materials
77.80.B- Phase transitions and Curie point
71.20.Ps Other inorganic compounds
77.22.Ch Permittivity (dielectric function)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Active laser ranging over planetary distances with millimeter accuracy

Yijiang Chen, Kevin M. Birnbaum, and Hamid Hemmati

Appl. Phys. Lett. 102, 241107 (2013); http://dx.doi.org/10.1063/1.4810906 (5 pages)

Online Publication Date: 18 June 2013

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Precision laser ranging between planetary bodies will allow advances in the study of fundamental physics and solar system dynamics. Current precision ranging techniques based on retro-reflectors are limited to the Earth-Moon distance. We present a method of active laser ranging over interplanetary distances with asynchronous two-way ranging. The method is validated in real time laboratory experiments and field tests. Sub-millimeter accuracy has been achieved in real-time active laser ranging for interplanetary distances, providing precision improvement well above three orders of magnitude over the current RF techniques. An instrument developed with the approach and deployed in future planetary missions will significantly advance planetary sciences and fundamental physics. For example, implemented in a future Mars lander mission our approach will clarify the Mars interior (liquid or solid), which is still an open question due to limitation of RF ranging precision although extensive efforts have been made over years with numerous missions since 1970s.
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96.30.Gc Mars
95.55.Pe Lunar, planetary, and deep-space probes
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Tuning the charge carriers in epitaxial graphene on SiC(0001) from electron to hole via molecular doping with C60F48

A. Tadich, M. T. Edmonds, L. Ley, F. Fromm, Y. Smets, Z. Mazej, J. Riley, C. I. Pakes, Th. Seyller, and M. Wanke

Appl. Phys. Lett. 102, 241601 (2013); http://dx.doi.org/10.1063/1.4811248 (5 pages)

Online Publication Date: 17 June 2013

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We demonstrate that the intrinsic electron doping of monolayer epitaxial graphene on SiC(0001) can be tuned in a controlled fashion to holes via molecular doping with the fluorinated fullerene C60F48. In situ angle-resolved photoemission is used to measure an upward shift of (0.6 ± 0.05) eV in the Dirac point from −0.43 eV to +0.17 eV relative to the Fermi level. The carrier density is observed to change from n ∼ (1 × 1013 ± 0.1 × 1013) cm−2 to p ∼ (2 × 1012 ± 1 × 1012) cm−2. We introduce a doping model employing Fermi-Dirac statistics which explicitly takes temperature and the highly correlated nature of molecular orbitals into account. The model describes the observed doping behaviour in our experiment and readily explains why net p-type doping was not achieved in a previous study [Coletti et al., Phys. Rev. B 81, 8 (2010)] which used tetrafluorotetra-cyanoquinodimethane (F4-TCNQ).
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
79.60.Bm Clean metal, semiconductor, and insulator surfaces
73.22.Pr Electronic structure of graphene

Organophosphonates as model system for studying electronic transport through monolayers on SiO2/Si surfaces

A. Bora, A. Pathak, K.-C. Liao, M. I. Vexler, A. Kuligk, A. Cattani-Scholz, B. Meinerzhagen, G. Abstreiter, J. Schwartz, and M. Tornow

Appl. Phys. Lett. 102, 241602 (2013); http://dx.doi.org/10.1063/1.4811441 (5 pages)

Online Publication Date: 17 June 2013

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We report electrical transport measurements made on alkylphosphonate self-assembled monolayers grown on nanometer-thin SiO2 on top of highly p-doped silicon. At small bias direct tunneling is characterized by a decay constant of β ≈ 0.7/carbon. At larger positive bias to the silicon (1.1–1.5 V) the current-voltage traces feature a prominent shoulder, reminiscent of a negative differential resistance. We attribute this feature to a significant reduction in trap-assisted tunneling, as supported by a simulation. Hence, organophosphonate monolayers are excellent model systems to study electrical transport through ordered structures; they also provide highly efficient electrical passivation of the SiO2/Si surface.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
73.40.Gk Tunneling
73.61.Ph Polymers; organic compounds

Band offsets and dielectric properties of the amorphous Si3N4/Si(100) interface: A first-principles study

T. Anh Pham, Tianshu Li, Huy-Viet Nguyen, Sadasivan Shankar, Francois Gygi, and Giulia Galli

Appl. Phys. Lett. 102, 241603 (2013); http://dx.doi.org/10.1063/1.4811481 (4 pages)

Online Publication Date: 17 June 2013

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By combining classical and ab-initio simulations, we generated a structural model of an amorphous silicon nitride/silicon(100) interface and we investigated its electronic and dielectric properties from first principles. We computed the valence band offset using many-body perturbation theory, within the GW approximation, and we found results in good agreement with experiments. Based on the computed local band edges and dielectric constants, we estimate that bulk properties are recovered for nitride films with thickness larger than 6–7 Å.
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73.40.-c Electronic transport in interface structures
77.22.Ch Permittivity (dielectric function)
61.43.Er Other amorphous solids
71.15.-m Methods of electronic structure calculations

Direct observation of charge transfer region at interfaces in graphene devices

Naoka Nagamura, Koji Horiba, Satoshi Toyoda, Shodai Kurosumi, Toshihiro Shinohara, Masaharu Oshima, Hirokazu Fukidome, Maki Suemitsu, Kosuke Nagashio, and Akira Toriumi

Appl. Phys. Lett. 102, 241604 (2013); http://dx.doi.org/10.1063/1.4808083 (5 pages)

Online Publication Date: 17 June 2013

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Nanoscale spectromicroscopic characterizing technique is indispensable for realization of future high-speed graphene transistors. Highly spatially resolved soft X-ray photoelectron microscopy measurements have been performed using our “3D nano-ESCA” (three-dimensional nanoscale electron spectroscopy for chemical analysis) equipment in order to investigate the local electronic states at interfaces in a graphene device structure. We have succeeded in detecting a charge transfer region at the graphene/metal-electrode interface, which extends over ∼500 nm with the energy difference of 60 meV. Moreover, a nondestructive depth profiling reveals the chemical properties of the graphene/SiO2-substrate interface.
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81.05.ue Graphene
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
72.80.Vp Electronic transport in graphene

Statistical properties of the electrically induced contact resistance between two stainless steel balls

Sang-Kuk Kim, Jae Sung Lee, Han Kwak, Sung-Oong Kang, Jongjin Lee, and In-Suk Yu

Appl. Phys. Lett. 102, 241605 (2013); http://dx.doi.org/10.1063/1.4811354 (5 pages)

Online Publication Date: 18 June 2013

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The electrical contact resistance between two stainless steel balls was measured to study the electrical conduction of a metallic contact separated by a thin oxide layer. Through a statistical approach, the contact resistance was found to have a bimodal log-normal distribution. This result reflects conduction by tunneling and electrically induced metal bridge, which was explained by the simulation of a random circuit breaker model, inside the insulating layer. Based on the results of this study, we suggest an effective conduction model to explain macroscopic electrical contact systems with a nano- or microscopic filamentary conduction mechanism.
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81.05.Bx Metals, semimetals, and alloys
73.40.Cg Contact resistance, contact potential
84.32.Dd Connectors, relays, and switches
73.40.Gk Tunneling

On applications and limitations of one-dimensional capillarity formulations for media with heterogeneous wettability

T. M. Bucher and H. Vahedi Tafreshi

Appl. Phys. Lett. 102, 241606 (2013); http://dx.doi.org/10.1063/1.4811167 (4 pages)

Online Publication Date: 18 June 2013

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Force-balance-based one-dimensional algebraic formulations that are often used in characterizing the capillarity of a multi-component system (e.g., predicting capillary height rise in porous media) are discussed. It is shown that such formulations fail to provide accurate predictions when the distribution of wetting (or non-wetting) surfaces is not homogeneous. A more general mathematical formulation is suggested and used to demonstrate that for media with heterogeneous wettability, hydrophilic (or hydrophobic) surfaces clustered in groups will have less contribution to the overall capillarity of the system.
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68.08.Bc Wetting
68.03.Cd Surface tension and related phenomena
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Mechanical response of polar/non-polar ZnO under low dimensional stress

T. H. Sung, J. C. Huang, and H. C. Chen

Appl. Phys. Lett. 102, 241901 (2013); http://dx.doi.org/10.1063/1.4811554 (4 pages)

Online Publication Date: 17 June 2013

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The mechanical properties of high quality polar (c-plane) and non-polar (a-plane and m-plane) ZnO wafers were examined by using nanoindentation and microcompression testing. The nano-scaled modulus, hardness, and yield strength readings of the c-plane, a-plane and m-plane ZnO wafers determined by nanoindentation are 140, 159, and 161; 7.1, 3.9, and 4.0; and 12.0, 6.7, and 4.5 GPa, respectively. The micro-scaled data directly measured by microcompression are much lower than the nano-scaled data. The cathodoluminescence images are in consistence with the slip systems observed from the transmission electron microscopy characterization.
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62.20.Qp Friction, tribology, and hardness
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
81.40.Lm Deformation, plasticity, and creep
62.20.fg Shape-memory effect; yield stress; superelasticity
78.60.Hk Cathodoluminescence, ionoluminescence
81.40.Jj Elasticity and anelasticity, stress-strain relations

Room temperature electrically tunable terahertz Faraday effect

A. Shuvaev, A. Pimenov, G. V. Astakhov, M. Mühlbauer, C. Brüne, H. Buhmann, and L. W. Molenkamp

Appl. Phys. Lett. 102, 241902 (2013); http://dx.doi.org/10.1063/1.4811496 (4 pages)

Online Publication Date: 18 June 2013

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We demonstrate electrical control of the room temperature Faraday effect in a 100-nm-thick film of strained HgTe, which is a topological insulator. The terahertz (THz) response of our device is dominated by the Drude response of carriers with high mobility. The electrical control is achieved by gating the carrier density in a static magnetic field, opening new perspectives for applications like high-speed amplitude and phase modulators in the THz frequency range.
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78.20.Ls Magneto-optical effects
78.70.Gq Microwave and radio-frequency interactions
72.20.Fr Low-field transport and mobility; piezoresistance

Interrupted interface growth and periodic boundary layer trapping in dendrite growth of steel

Xiaoping Ma and Dianzhong Li

Appl. Phys. Lett. 102, 241903 (2013); http://dx.doi.org/10.1063/1.4811701 (5 pages)

Online Publication Date: 18 June 2013

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The time continuity, spatial continuity, and segregation are investigated in the directional solidified columnar dendrite with pulling velocity 40 μm/s and quenching solidified columnar dendrite of 20SiMn and 20SiMnMo steel. The results show that the growth of columnar dendrite is a dynamic discrete process with interrupted interface growth and periodic trapping of solute enriched boundary layer in growing austenite dendrite matrix. Theoretical analysis shows that the non-equilibrium solute partition at the growing interface and actual temperature gradient accounts for above phenomena. Such growth style results in the segregationless dendrite in the mesoscale.
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68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
81.30.Mh Solid-phase precipitation
81.30.Fb Solidification
81.40.Gh Other heat and thermomechanical treatments
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Near-ideal electrical properties of InAs/WSe2 van der Waals heterojunction diodes

Steven Chuang, Rehan Kapadia, Hui Fang, Ting Chia Chang, Wen-Chun Yen, Yu-Lun Chueh, and Ali Javey

Appl. Phys. Lett. 102, 242101 (2013); http://dx.doi.org/10.1063/1.4809815 (4 pages)

Online Publication Date: 17 June 2013

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Here, we present the fabrication and electrical analysis of InAs/WSe2 van der Waals heterojunction diodes formed by the transfer of ultrathin membranes of one material upon another. Notably, InAs and WSe2 are two materials with completely different crystal structures, which heterojunction is inconceivable with traditional epitaxial growth techniques. Clear rectification from the n-InAs/p-WSe2 junction (forward/reverse current ratio >106) is observed. A low reverse bias current <10−12A/μm2 and ideality factor of ∼1.1 were achieved, suggesting near-ideal electrically active interfaces.
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85.30.Kk Junction diodes
61.66.Fn Inorganic compounds
68.55.ag Semiconductors
73.40.Ei Rectification
81.05.Ea III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Enhancement of bias and illumination stability in thin-film transistors by doping InZnO with wide-band-gap Ta2O5

Linfeng Lan (兰林锋), Nana Xiong, Peng Xiao, Min Li, Hua Xu, Rihui Yao, Shangsheng Wen, and Junbiao Peng

Appl. Phys. Lett. 102, 242102 (2013); http://dx.doi.org/10.1063/1.4811416 (4 pages)

Online Publication Date: 18 June 2013

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Thin-film transistor (TFT) with Ta2O5-doped InZnO (TIZO) channel layer was demonstrated. The TIZO-TFT exhibited smaller subthreshold swing and higher capability of carrier controlling when bearing nitrogen pre-annealing than the InZnO-TFT. Detailed studies showed that Ta had an effect of suppressing oxygen out-diffusing during thermal annealing, resulting in improving of the stability under positive gate bias stress. Furthermore, the TIZO-TFT displayed better stability under light illumination than InZnO-TFT, owing to its wider band gap and lower absorption after doped with wider-band-gap Ta2O5.
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85.30.Tv Field effect devices

Doping dependence of self-diffusion in germanium and the charge states of vacancies

T. Südkamp, H. Bracht, G. Impellizzeri, J. Lundsgaard Hansen, A. Nylandsted Larsen, and E. E. Haller

Appl. Phys. Lett. 102, 242103 (2013); http://dx.doi.org/10.1063/1.4811442 (4 pages)

Online Publication Date: 18 June 2013

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Self-diffusion in boron-doped germanium has been studied at temperatures between 526 and 749 °C with secondary ion mass spectrometry. Self-diffusion under acceptor doping is retarded compared to intrinsic conditions. This demonstrates the contribution of charged vacancies in self-diffusion. Taking into account the dominance of doubly negatively charged vacancies under donor doping, the doping dependence of self-diffusion is best described with an inverse level ordering for singly and doubly negatively charged vacancies for all doping conditions. The level ordering explains the dominance of doubly charged vacancies under donor doping and their decreasing contribution with increasing acceptor doping until neutral vacancies mediate self-diffusion.
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66.30.H- Self-diffusion and ionic conduction in nonmetals
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
61.72.jd Vacancies
61.72.uf Ge and Si

Observation of optical spin injection into Ge-based structures at room temperature

Yuhsuke Yasutake, Shuhei Hayashi, Hiroyuki Yaguchi, and Susumu Fukatsu

Appl. Phys. Lett. 102, 242104 (2013); http://dx.doi.org/10.1063/1.4811495 (4 pages)

Online Publication Date: 18 June 2013

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Non-zero spin polarization induced by optical orientation was clearly observed at room temperature in a Ge/Ge0.8Si0.2 quantum well grown on Ge and a Ge layer grown on Si by molecular beam epitaxy, whereas it was absent in bulk Ge. This occurred because indirect-gap photoluminescence (PL), which can obscure the spin-polarization information carried by the direct-gap PL, was quenched by unintentional growth-related defects in the epitaxial layers. Such interpretation was confirmed by applying time gating that effectively removed the indirect-gap PL characterized by a slower rise time, which allowed us to demonstrate the existence of room-temperature spin polarization in bulk Ge.
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72.25.Dc Spin polarized transport in semiconductors
72.25.Mk Spin transport through interfaces
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
78.67.De Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Wavelength limits for InGaN quantum wells on GaN

Markus Pristovsek

Appl. Phys. Lett. 102, 242105 (2013); http://dx.doi.org/10.1063/1.4811560 (3 pages)

Online Publication Date: 18 June 2013

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The emission wavelength of coherently strained InGaN quantum wells (QW) is limited by the maximum thickness before relaxation starts. For high indium contents x>40% the resulting wavelength decreases because quantum confinement dominates. For low indium content x<40% the electron hole wave function overlap (and hence radiative emission) is strongly reduced with increasing QW thickness due to the quantum confined Stark effect and imposes another limit. This results in a maximum usable emission wavelength at around 600 nm for QWs with 40%-50% indium content. Relaxed InGaN buffer layers could help to push this further, especially on non- and semi-polar orientations.
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78.67.De Quantum wells
68.65.Fg Quantum wells
78.20.Jq Electro-optical effects
68.55.jd Thickness

The impact of negative oxygen ion bombardment on electronic and structural properties of magnetron sputtered ZnO:Al films

André Bikowski, Thomas Welzel, and Klaus Ellmer

Appl. Phys. Lett. 102, 242106 (2013); http://dx.doi.org/10.1063/1.4811647 (4 pages)

Online Publication Date: 18 June 2013

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In order to study the impact of negative oxygen ion bombardment on the electronic transport properties of ZnO:Al films, a systematic magnetron sputtering study from ceramic targets with excitation frequencies from DC to 27 MHz, accompanied by strongly varying discharge voltages, has been performed. Higher plasma excitation frequencies significantly improve the transport properties of ZnO:Al films. The effect of the bombardment of the films by energetic particles (negative oxygen ions) can be explained by the dynamic equilibrium between the formation of acceptor-like oxygen interstitials compensating the extrinsic donors and the self-annealing of the interstitial defects at higher deposition temperatures.
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73.61.Ga II-VI semiconductors
61.80.Jh Ion radiation effects
81.15.Cd Deposition by sputtering
68.55.ag Semiconductors
61.72.jj Interstitials
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
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Evidence of an embedded vortex translation mode in flake-shaped ferromagnetic particle composites

J. Neige, T. Lepetit, N. Malléjac, A.-L. Adenot-Engelvin, A. Thiaville, and N. Vukadinovic

Appl. Phys. Lett. 102, 242401 (2013); http://dx.doi.org/10.1063/1.4811375 (4 pages)

Online Publication Date: 17 June 2013

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A low-frequency resonance (sub-GHz) is observed in microwave permeability spectra of anisotropic flake-shaped ferromagnetic particle composites. The resonance frequency of this peak increases linearly with the saturation magnetization of flakes, their aspect ratio, and the amplitude of a perpendicular static magnetic field. In addition, this resonance becomes extinct for a perpendicular RF exciting magnetic field. These experimental features are reproduced by an analytical model of vortex dynamics which militates in favor of an assignment of this low-frequency signal as an embedded vortex translation mode within a multidomain magnetic structure.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Tt Fine-particle systems; nanocrystalline materials
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)

Distinguishing spin pumping from spin rectification in a Pt/Py bilayer through angle dependent line shape analysis

Lihui Bai, Z. Feng, P. Hyde, H. F. Ding, and C.-M. Hu

Appl. Phys. Lett. 102, 242402 (2013); http://dx.doi.org/10.1063/1.4811482 (3 pages)

Online Publication Date: 17 June 2013

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A pure spin current driven by spin pumping is converted to a DC voltage and detected electrically in a Py/Pt bilayer sample. This DC voltage mixes with a DC voltage produced through spin rectification. The ferromagnetic resonance line shape strongly depends on the microwave magnetic h field distribution. We have systematically studied the line shapes by changing the external magnetic field orientation in plane of a Pt/Py bilayer. A method is demonstrated which allows us to calculate the microwave h field vector distribution, and distinguish spin pumping from spin rectification.
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81.05.Bx Metals, semimetals, and alloys
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
72.25.-b Spin polarized transport
73.40.Ei Rectification
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance

Hydrogen adsorption promoted perpendicular magnetic anisotropy in nano-structured Fe coverage on Pd/W{112} faceting surface

Chieh-Chen Chiu, Wen-Chin Lin, Yu-Chen Yeh, and Ker-Jar Song

Appl. Phys. Lett. 102, 242403 (2013); http://dx.doi.org/10.1063/1.4811492 (5 pages)

Online Publication Date: 17 June 2013

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Nano-structured Fe coverage was deposited on Pd/W{112} faceting surface for the investigation of magnetic properties. The morphology consisting of 3-sided nano-pyramids in Fe coverage remained stable at least up to 400 K. The Fe magnetization switched from perpendicular to in-plane direction at 2 physical monolayer (PML). Hydrogen adsorption significantly enhanced the perpendicular coercivity by 6-7 times, and shifted the switching critical thickness to 2.8 PML. The hydrogen thermal desorption and re-adsorption seriously influenced the magnetic behaviors, depending on the hydrogen partial pressure.
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68.43.Mn Adsorption kinetics
75.30.Gw Magnetic anisotropy
75.50.Tt Fine-particle systems; nanocrystalline materials
75.75.Cd Fabrication of magnetic nanostructures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.43.Nr Desorption kinetics
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