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7 May 2012

Volume 100, Issue 19, Articles (19xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 191901 (2012); http://dx.doi.org/10.1063/1.4709436 (4 pages)

Muamer Kadic, Tiemo Bückmann, Nicolas Stenger, Michael Thiel, and Martin Wegener
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Optical phonon lifetimes in sputtered AlN thin films

P. Pobedinskas, B. Ruttens, J. D’Haen, and K. Haenen

Appl. Phys. Lett. 100, 191906 (2012); http://dx.doi.org/10.1063/1.4711773 (4 pages) | Cited 1 time

Online Publication Date: 8 May 2012

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We study the vibrational properties of AlN thin films deposited on silicon (100) substrates by the reactive DC-pulsed magnetron sputtering. The frequencies and lifetimes of the E1(TO) and A1(LO) optical phonons are calculated from Fourier transform infrared spectra using the factorized model of a damped oscillator. We analyze the structural properties by the x-ray diffraction technique to correlate the elongation of phonon lifetimes with increasing film thickness. The lifetimes of the phonon modes in AlN thin films are compared to the values in a single crystal.
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63.22.Dc Free films
68.55.ag Semiconductors
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
81.15.Cd Deposition by sputtering

Oxygen transport and GeO2 stability during thermal oxidation of Ge

S. R. M. da Silva, G. K. Rolim, G. V. Soares, I. J. R. Baumvol, C. Krug, L. Miotti, F. L. Freire, Jr., M. E. H. M. da Costa, and C. Radtke

Appl. Phys. Lett. 100, 191907 (2012); http://dx.doi.org/10.1063/1.4712619 (4 pages)

Online Publication Date: 9 May 2012

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Oxygen transport during thermal oxidation of Ge and desorption of the formed Ge oxide are investigated. Higher oxidation temperatures and lower oxygen pressures promote GeO desorption. An appreciable fraction of oxidized Ge desorbs during the growth of a GeO2 layer. The interplay between oxygen desorption and incorporation results in the exchange of O originally present in GeO2 by O from the gas phase throughout the oxide layer. This process is mediated by O vacancies generated at the GeO2/Ge interface. The formation of a substoichiometric oxide is shown to have direct relation with the GeO desorption.
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81.65.Mq Oxidation
68.43.Nr Desorption kinetics

Broadband transmission enhancement of acoustic waves through a hybrid grating

Chunyin Qiu, Rui Hao, Feng Li, Shengjun Xu, and Zhengyou Liu

Appl. Phys. Lett. 100, 191908 (2012); http://dx.doi.org/10.1063/1.4714719 (4 pages) | Cited 1 time

Online Publication Date: 9 May 2012

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We report an anomalous transmission enhancement of acoustic waves through a hybrid grating. The fundamental physics behind this phenomenon can be captured well by the improved impedance matching between the hybrid grating and the background fluid. This type of acoustic transparency is broadband and can be robust against the incident angle, which is drastically different from the previously reported mechanisms that are closely related with resonances. Potential applications of this effect can be anticipated in ultrasonic devices.
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43.20.-f General linear acoustics

Nanoscale quantification of octahedral tilts in perovskite films

Jinwoo Hwang, Jack Y. Zhang, Junwoo Son, and Susanne Stemmer

Appl. Phys. Lett. 100, 191909 (2012); http://dx.doi.org/10.1063/1.4714734 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2012

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NiO6-octahedral tilts in ultrathin LaNiO3 films were studied using position averaged convergent beam electron diffraction (PACBED) in scanning transmission electron microscopy. Both the type and magnitude of the octahedral tilts were determined by comparing PACBED experiments to frozen phonon multislice simulations. It is shown that the out-of-plane octahedral tilt of an epitaxial film under biaxial tensile stress (0.78% in-plane tensile strain) increases by ∼20%, while the in-plane rotation decreases by ∼80%, compared to the unstrained bulk material.
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68.55.-a Thin film structure and morphology
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Mechanisms of fragmentation of aluminum-tungsten granular composites under dynamic loading

K. L. Olney, V. F. Nesterenko, and D. J. Benson

Appl. Phys. Lett. 100, 191910 (2012); http://dx.doi.org/10.1063/1.4711768 (4 pages)

Online Publication Date: 9 May 2012

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Numerical simulations of aluminum (Al) and tungsten (W) granular composite rings under various dynamic loading conditions due to explosive loading were performed. Three competing mechanisms of fragmentation were observed: a continuum level mechanism generating macrocracks with a size scale comparable to the case width, a mesoscale mechanism generating voids and microcracks at the unbonded Al/W interfaces due to tensile strains, and mesoscale jetting due to the development of large velocity gradients between the W particles and surrounding Al. These mesoscale mechanisms can be used to tailor the size of the fragments (macro to mesoscale) by selecting an appropriate initial mesostructure for a given loading condition.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.mt Cracks
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Sequential three-step three-photon near-infrared quantum splitting in β-NaYF4:Tm3+

D. C. Yu, S. Ye, M. Y. Peng, Q. Y. Zhang, and L. Wondraczek

Appl. Phys. Lett. 100, 191911 (2012); http://dx.doi.org/10.1063/1.4714505 (4 pages) | Cited 4 times

Online Publication Date: 10 May 2012

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We report on sequential three-step three-photon near-infrared (NIR) quantum splitting in Tm3+-doped β-NaYF4, where an incident blue photon around 470 nm is split into three NIR photons (1165, 1466, and 1800 nm). The underlying mechanism is analyzed by means of static and dynamic photoemission spectroscopy. Here, an experimental total quantum yield of ∼32% is obtained. When quenching due to residual hydroxyl groups and other defect species can be overcome, numerical analyses indicate a theoretical maximum quantum yield of 158%, suggesting application in efficient spectral converters.
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78.55.Hx Other solid inorganic materials
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.40.Gh Other heat and thermomechanical treatments

Nanocrystalline-to-amorphous transition in nanolaminates grown by low temperature atomic layer deposition and related mechanical properties

R. Raghavan, M. Bechelany, M. Parlinska, D. Frey, W. M. Mook, A. Beyer, J. Michler, and I. Utke

Appl. Phys. Lett. 100, 191912 (2012); http://dx.doi.org/10.1063/1.4711767 (4 pages) | Cited 2 times

Online Publication Date: 10 May 2012

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We report on a comprehensive structural and nanoindentation study of nanolaminates of Al2O3 and ZnO synthesized by atomic layer deposition (ALD). By reducing the bilayer thickness from 50 nm to below 1 nm, the nanocrystal size could be controlled in the nanolaminate structure. The softer and more compliant response of the multilayers as compared to the single layers of Al2O3 and ZnO is attributed to the structural change from nanocrystalline to amorphous at smaller bilayer thicknesses. It is also shown that ALD is a unique technique for studying the inverse Hall-Petch softening mechanism (E. Voce and D. Tabor, J. Inst. Metals 79(12), 465 (1951)) related to grain size effects in nanomaterials.
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81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
81.40.Lm Deformation, plasticity, and creep
62.20.fg Shape-memory effect; yield stress; superelasticity
64.70.K- Solid-solid transitions
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Stretch-induced softening of bending rigidity in graphene

Xinghua Shi, Bo Peng, Nicola M. Pugno, and Huajian Gao

Appl. Phys. Lett. 100, 191913 (2012); http://dx.doi.org/10.1063/1.4716024 (5 pages) | Cited 3 times

Online Publication Date: 10 May 2012

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First principle calculations are performed to show that the bending rigidity of graphene can be softened considerably with in-plane stretching. This phenomenon can be attributed to stretch-induced loosening of atomic packing and should be of fundamental significance for graphene-based structures and devices.
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81.40.Lm Deformation, plasticity, and creep
62.20.de Elastic moduli
62.20.F- Deformation and plasticity
61.48.Gh Structure of graphene
81.05.ue Graphene
81.40.Jj Elasticity and anelasticity, stress-strain relations

On the origin of the 265 nm absorption band in AlN bulk crystals

Ramón Collazo, Jinqiao Xie, Benjamin E. Gaddy, Zachary Bryan, Ronny Kirste, Marc Hoffmann, Rafael Dalmau, Baxter Moody, Yoshinao Kumagai, Toru Nagashima, Yuki Kubota, Toru Kinoshita, Akinori Koukitu, Douglas L. Irving, and Zlatko Sitar

Appl. Phys. Lett. 100, 191914 (2012); http://dx.doi.org/10.1063/1.4717623 (5 pages) | Cited 3 times

Online Publication Date: 10 May 2012

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Single crystal AlN provides a native substrate for Al-rich AlGaN that is needed for the development of efficient deep ultraviolet light emitting and laser diodes. An absorption band centered around 4.7 eV (∼265 nm) with an absorption coefficient above 1000 cm−1 is observed in these substrates. Based on density functional theory calculations, substitutional carbon on the nitrogen site introduces absorption at this energy. A series of single crystalline wafers were used to demonstrate that this absorption band linearly increased with carbon, strongly supporting the model that CN- is the predominant state for carbon in AlN.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Fy Semiconductors

Sub-0.1 nm-resolution quantitative scanning transmission electron microscopy without adjustable parameters

C. Dwyer, C. Maunders, C. L. Zheng, M. Weyland, P. C. Tiemeijer, and J. Etheridge

Appl. Phys. Lett. 100, 191915 (2012); http://dx.doi.org/10.1063/1.4711766 (4 pages) | Cited 5 times

Online Publication Date: 11 May 2012

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Atomic-resolution imaging in the scanning transmission electron microscope (STEM) constitutes a powerful tool for nanostructure characterization. Here, we demonstrate the quantitative interpretation of atomic-resolution high-angle annular dark-field (ADF) STEM images using an approach that does not rely on adjustable parameters. We measure independently the instrumental parameters that affect sub-0.1 nm-resolution ADF images, quantify their individual and collective contributions to the image intensity, and show that knowledge of these parameters enables a quantitative interpretation of the absolute intensity and contrast across all accessible spatial frequencies. The analysis also provides a method for the in-situ measurement of the STEM’s effective source distribution.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
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Low temperature fabrication and characterization of nickel germanide Schottky source/drain contacts for implant-less germanium p-channel metal-oxide-semiconductor field-effect transistors

D. R. Gajula, D. W. McNeill, B. E. Coss, H. Dong, S. Jandhyala, J. Kim, R. M. Wallace, and B. M. Armstrong

Appl. Phys. Lett. 100, 192101 (2012); http://dx.doi.org/10.1063/1.4712564 (3 pages)

Online Publication Date: 8 May 2012

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In this work, nickel germanide Schottky contacts have been fabricated on n-type germanium (n-Ge) with an optimum barrier height of 0.63 eV. For rapid thermal annealing (RTA) temperatures above 300  °C, all phases of nickel and germanium convert to nickel mono-germanide (NiGe). However, higher RTA temperatures are also found to cause agglomeration of the NiGe phase and higher leakage current. So, the optimum temperature for Schottky-based source/drain contact formation on n-Ge is ∼300 °C, where the nickel mono-germanide phase is formed but without phase agglomeration.
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73.30.+y Surface double layers, Schottky barriers, and work functions
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Flexible thin-film InAs/GaAs quantum dot solar cells

Katsuaki Tanabe, Katsuyuki Watanabe, and Yasuhiko Arakawa

Appl. Phys. Lett. 100, 192102 (2012); http://dx.doi.org/10.1063/1.4712597 (4 pages) | Cited 2 times

Online Publication Date: 8 May 2012

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Thin-film InAs/GaAs quantum dot (QD) solar cells on mechanically flexible plastic films are fabricated. A 4.1-μm-thick compound semiconductor photovoltaic layer grown on a GaAs substrate is transferred onto a plastic film through a low-temperature bonding technique. We also fabricate thin-film InAs/GaAs quantum dot solar cells on Si substrates, as alternative low-cost, lightweight, robust substrates. The open-circuit voltages of the thin-film cells on plastic and Si substrates are equal to that of the as-grown bulk cell on a GaAs substrate, indicating that no material degradation occurs during our bond-and-transfer process.
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88.40.H- Solar cells (photovoltaics)

Raman analysis of monoclinic Cu2SnS3 thin films

Dominik M. Berg, Rabie Djemour, Levent Gütay, Susanne Siebentritt, Phillip J. Dale, Xavier Fontane, Victor Izquierdo-Roca, and Alejandro Pérez-Rodriguez

Appl. Phys. Lett. 100, 192103 (2012); http://dx.doi.org/10.1063/1.4712623 (4 pages) | Cited 5 times

Online Publication Date: 8 May 2012

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Secondary phases like Cu2SnS3 are major obstacles for kesterite thin film solar cell applications. We prepare Cu2SnS3 using identical annealing conditions as used for the kesterite films. By x-ray diffraction, the crystal structure of Cu2SnS3 was identified as monoclinic. Polarization-dependent Raman investigations allowed the identification of the dominant peaks at 290 cm−1 and 352 cm−1 with the main A′ symmetry vibrational modes from the monoclinic Cu2SnS3 phase. Furthermore, micro-resolved Raman investigations revealed local variations in the spectra that are attributed to a secondary phase (possibly Cu2Sn3S7). This exemplifies the abilities of micro-resolved Raman measurements in the detection of secondary phases.
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78.66.Li Other semiconductors
68.55.ag Semiconductors
61.72.Cc Kinetics of defect formation and annealing
78.30.Hv Other nonmetallic inorganics

Millimeter wave transmission spectroscopy of gated two-dimensional hole systems

K. Stone, R. R. Du, M. J. Manfra, L. N. Pfeiffer, and K. W. West

Appl. Phys. Lett. 100, 192104 (2012); http://dx.doi.org/10.1063/1.4711772 (3 pages)

Online Publication Date: 8 May 2012

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We developed a differential transmission to study cyclotron resonance of GaAs/AlxGa1−xAs two-dimensional hole samples. The technique utilizes a modulated AuPd gate isolated by a Si3 N4 dielectric from the sample, which is irradiated opposite the gate by millimeter waves ranging from 2 to 40 GHz. This technique effectively removes the background signal and yields a hole effective mass of 0.41me with a cyclotron scattering time of ∼20 ps, consistent with the previous results using different techniques.
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76.40.+b Diamagnetic and cyclotron resonances
78.70.Gq Microwave and radio-frequency interactions
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Spin-polarized two-dimensional electron gas in undoped MgxZn1−xO/ZnO heterostructures

K. Han, N. Tang, J. D. Ye, J. X. Duan, Y. C. Liu, K. L. Teo, and B. Shen

Appl. Phys. Lett. 100, 192105 (2012); http://dx.doi.org/10.1063/1.4711775 (4 pages) | Cited 1 time

Online Publication Date: 8 May 2012

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Quantum transport properties of two-dimensional electron gas (2DEG) in undoped MgxZn1−xO/ZnO heterostructures grown by metal organic vapor phase epitaxy have been investigated. A large zero-field spin-splitting energy more than 15 meV in the 2DEG is determined at 1.6 K. Meanwhile, ferromagnetism is observed in the heterostructures. The findings reveal that the 2DEG is spin polarized at zero magnetic fields. It is believed that the exchange interaction between the itinerant electrons in the two-dimensional channel and the magnetic polarons in the MgxZn1−xO barrier around the interface results in the spin polarization of the 2DEG.
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81.05.Dz II-VI semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
72.25.Dc Spin polarized transport in semiconductors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
75.50.Pp Magnetic semiconductors

Optimization of AlAs/AlGaAs quantum well heterostructures on on-axis and misoriented GaAs (111)B

F. Herzog, M. Bichler, G. Koblmüller, S. Prabhu-Gaunkar, W. Zhou, and M. Grayson

Appl. Phys. Lett. 100, 192106 (2012); http://dx.doi.org/10.1063/1.4711783 (5 pages)

Online Publication Date: 8 May 2012

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We report systematic growth optimization of high Al-content AlGaAs, AlAs, and associated modulation-doped quantum well (QW) heterostructures on on-axis and misoriented GaAs (111)B by molecular beam epitaxy. Growth temperatures TG > 690 °C and low As4 fluxes close to group III-rich growth significantly suppress twin defects in high-Al content AlGaAs on on-axis GaAs (111)B, as quantified by atomic force and transmission electron microscopy as well as x-ray diffraction. Mirror-smooth and defect-free AlAs with pronounced step-flow morphology was further achieved by growth on 2° misoriented GaAs (111)B toward [0math1] and [2mathmath] orientations. Successful fabrication of modulation-doped AlAs QW structures on these misoriented substrates yielded record electron mobilities (at 1.15 K) in excess of 13 000 cm2/Vs at sheet carrier densities of 5 × 1011 cm−2.
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68.55.ag Semiconductors
72.20.Ee Mobility edges; hopping transport
72.20.Fr Low-field transport and mobility; piezoresistance
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.63.Hs Quantum wells
81.05.Ea III-V semiconductors
81.07.St Quantum wells

High-power 2.0 µm semiconductor disk laser—Influence of lateral lasing

Tino Töpper, Marcel Rattunde, Sebastian Kaspar, Rüdiger Moser, Christian Manz, Klaus Köhler, and Joachim Wagner

Appl. Phys. Lett. 100, 192107 (2012); http://dx.doi.org/10.1063/1.4714512 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2012

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The influence of lateral lasing on the high-power performance of 2 µm GaSb-based optically pumped semiconductor disk laser (SDL) has been investigated. The maximum cw output power of the SDL exceeded 4.1 W at 20 °C heat sink temperature. The occurrence of lateral lasing was observed by recording the emission spectrum and the emitted optical power in the in-plane direction of the SDL chip. We investigated the conditions for which lateral lasing occurs and demonstrate an effective means to suppress this unwanted phenomenon even for small SDL chip sizes comparable to the pump spot diameter.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Empirical modeling of the cross section of damage formation in ion implanted III-V semiconductors

E. Wendler and L. Wendler

Appl. Phys. Lett. 100, 192108 (2012); http://dx.doi.org/10.1063/1.4711810 (4 pages) | Cited 1 time

Online Publication Date: 9 May 2012

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In this letter, the cross section of damage formation per individual ion is measured for III-V compound semiconductors ion implanted at 15 K, applying Rutherford backscattering spectrometry. An empirical model is proposed that explains the measured cross sections in terms of quantities representing the primary energies deposited in the displacement of lattice atoms and in electronic interactions. The resulting formula allows the prediction of damage formation for low temperatures and low ion fluences in these materials and can be taken as a starting point for further quantitative modeling of damage formation including secondary effects such as temperature and ion flux.
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61.82.Fk Semiconductors
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
61.80.Jh Ion radiation effects

High fraction of substitutional phosphorus in a (100) diamond epilayer with low surface roughness

M.-A. Pinault-Thaury, B. Berini, I. Stenger, E. Chikoidze, A. Lusson, F. Jomard, J. Chevallier, and J. Barjon

Appl. Phys. Lett. 100, 192109 (2012); http://dx.doi.org/10.1063/1.4712617 (4 pages) | Cited 1 time

Online Publication Date: 10 May 2012

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For high power electronics, diamond is a promising semiconductor with phosphorus being the current substitutional donor. However, up to now, in (100) oriented grown diamond, only a small fraction of phosphorus atoms is incorporated in substitutional sites (<30%) and the epilayer surface exhibits macrosteps. In this work, we present a (100) phosphorus-doped diamond epilayer where ∼100% of the phosphorus atoms are incorporated in substitutional sites. The film exhibits a low surface roughness (RMS = 0.5 nm). Our epilayer is conductive (ρ = 5.0 × 106 Ω · cm at 300 K) and neutral phosphorus are detected in infrared absorption.
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68.35.bg Semiconductors
73.61.Cw Elemental semiconductors
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
78.66.Tr Fullerenes and related materials
81.05.Cy Elemental semiconductors

GaN epitaxy on Cu(110) by metal organic chemical vapor deposition

Qiming Li, Jeffery Figiel, George Wang, Huiwen Xu, and Ganesh Balakrishnan

Appl. Phys. Lett. 100, 192110 (2012); http://dx.doi.org/10.1063/1.4714738 (3 pages)

Online Publication Date: 10 May 2012

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We demonstrate that Cu can be a suitable substrate material for c-plane GaN epitaxy using metal organic chemical vapor deposition. By using a low temperature AlN buffer layer, Ga and Cu alloying can be prevented so that GaN layer can be grown on Cu at a temperature of 1000 °C. An epitaxial relation of GaN (0001)//Cu(110) is observed using cross-section transmission electron microscopy and electron back scatter diffraction studies. The single crystalline GaN epilayer shows a threading dislocation density of 3 × 109 cm−2 and strong band edge emission at room temperature. The site alignment between GaN (0001) and Cu(110) shows a mesh ratio of 4/3 and 5/3 in GaN [10-10] and GaN [-1100] directions, which is attributed to the epitaxial relation observed.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.ag Semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
79.20.Kz Other electron-impact emission phenomena
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Spin-polarization of VGaON center in GaN and its application in spin qubit

Xiaopeng Wang, Mingwen Zhao, Zhenhai Wang, Xiujie He, Yan Xi, and Shishen Yan

Appl. Phys. Lett. 100, 192401 (2012); http://dx.doi.org/10.1063/1.4712595 (4 pages) | Cited 1 time

Online Publication Date: 7 May 2012

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VGaON center in cubic gallium nitride is a defect complex composing of a substitutional oxygen atom at nitrogen site (ON) and an adjacent gallium vacancy (VGa). Based on first-principles calculations, we predicted that this VGaON center has much in common with the famous nitrogen-vacancy center in diamond, but the excitation energy is very low. The electron spin-polarization of the centers can be tuned by changing the charge states. The neutral ONVGa center has the v↓ and exy↓ states being well isolated from the bulk bands with appropriate spacing which are suitable for achieving spin qubit operation with low excitation energy.
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72.25.Dc Spin polarized transport in semiconductors
61.72.jd Vacancies
61.66.Fn Inorganic compounds
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations
71.20.Nr Semiconductor compounds
71.55.Eq III-V semiconductors

The comparison of direct and indirect methods for determining the magnetocaloric parameters in the Heusler alloy Ni50Mn34.8In14.2B

Igor Dubenko, Tapas Samanta, Abdiel Quetz, Alexander Kazakov, Igor Rodionov, Denis Mettus, Valerii Prudnikov, Shane Stadler, Philip Adams, Joseph Prestigiacomo, Alexander Granovsky, Arcady Zhukov, and Naushad Ali

Appl. Phys. Lett. 100, 192402 (2012); http://dx.doi.org/10.1063/1.4714539 (4 pages) | Cited 2 times

Online Publication Date: 7 May 2012

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The magnetocaloric properties of the Ni50Mn34.8In14.2B Heusler alloy have been studied by direct measurements of the adiabatic temperature change (ΔTAD(T,H)) and indirectly by magnetization (M(T,H)), differential scanning calorimetry, and specific heat (C(T,H)) measurements. The presence of a first-order ferromagnetic-paramagnetic transition has been detected for Ni50Mn34.8In14.2B at 320 K. The magnetocaloric parameters, i.e., the magnetic entropy change (ΔSM = (2.9-3.2) J/kgK) and the adiabatic temperature change (ΔTAD = (1.3-1.52) K), have been evaluated for ΔH = 1.8 T from CP(T,H) and M(T,H) data and from direct ΔTAD(T,H) measurements. The extracted magnetocaloric parameters are comparable to those of Gd.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Generation and annihilation of domain walls in nanowires by localized fields

Falk-Ulrich Stein, Lars Bocklage, Toru Matsuyama, and Guido Meier

Appl. Phys. Lett. 100, 192403 (2012); http://dx.doi.org/10.1063/1.4711222 (3 pages) | Cited 2 times

Online Publication Date: 7 May 2012

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We study the creation and annihilation of domain walls in a permalloy nanowire by local Oersted fields of current pulses passing through a perpendicularly aligned stripline. The occurrence of both processes is investigated for current pulses of different polarities and for various external magnetic fields. Reliable creation and annihilation are achieved for small and zero external fields, while higher externally applied fields lead to the suppression of both processes as well as to the creation of multiple domain walls in the wire.
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75.60.Ch Domain walls and domain structure
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
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)

Defect and adsorbate induced ferromagnetic spin-order in magnesium oxide nanocrystallites

Ashok Kumar, Jitendra Kumar, and Shashank Priya

Appl. Phys. Lett. 100, 192404 (2012); http://dx.doi.org/10.1063/1.4712058 (4 pages) | Cited 5 times

Online Publication Date: 8 May 2012

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We report the correlation between d0 ferromagnetism, photoluminescence (PL), and adsorbed hydrogen (H−) species in magnesium oxide (MgO) nanocrystallites. Our study suggests that the oxygen vacancies, namely singly ionized anionic vacancies (F+) and dimers (F22+) induce characteristic photoluminescence and the room-temperature ferromagnetic spin-order. Nanocrystallites with low population of oxygen vacancies have revealed diamagnetic behavior. Intriguingly, on adsorption of hydrogen (H−) species in the MgO nanocrystallites, ferromagnetic behavior was either enhanced (in the case of highly oxygen deficient nanocrystallites) or begun to percolate (in the case of nanocrystallite with low population density of oxygen vacancies).
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75.50.Tt Fine-particle systems; nanocrystalline materials
78.55.Hx Other solid inorganic materials
61.72.jd Vacancies
75.75.-c Magnetic properties of nanostructures
75.20.Ck Nonmetals
75.50.Dd Nonmetallic ferromagnetic materials

Antiferromagnetic domain wall engineering in chromium films

J. M. Logan, H. C. Kim, D. Rosenmann, Z. Cai, R. Divan, O. G. Shpyrko, and E. D. Isaacs

Appl. Phys. Lett. 100, 192405 (2012); http://dx.doi.org/10.1063/1.4712598 (4 pages) | Cited 1 time

Online Publication Date: 8 May 2012

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Show Abstract
We have engineered an antiferromagnetic domain wall by utilizing a magnetic frustration effect of a thin iron cap layer deposited on a chromium film. Through lithography and wet etching, we selectively remove areas of the Fe cap layer to form a patterned ferromagnetic mask over the Cr film. Removing the Fe locally removes magnetic frustration in user-defined regions of the Cr film. We present x-ray microdiffraction microscopy results confirming the formation of a 90° spin-density wave propagation domain wall in Cr. This domain wall nucleates at the boundary defined by our Fe mask.
Show PACS
75.60.Ch Domain walls and domain structure
81.65.Cf Surface cleaning, etching, patterning
75.50.Ee Antiferromagnetics
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Ds Spin waves
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