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14 Jan 2013

Volume 102, Issue 2, Articles (02xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 102, 023901 (2013); http://dx.doi.org/10.1063/1.4773526 (4 pages)

Yoshihiro Gohda and Shinji Tsuneyuki
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Giant low field magnetocaloric effect in soft ferromagnetic ErRuSi

Sachin B. Gupta and K. G. Suresh

Appl. Phys. Lett. 102, 022408 (2013); http://dx.doi.org/10.1063/1.4775690 (4 pages) | Cited 1 time

Online Publication Date: 15 January 2013

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The magnetic and magnetocaloric properties of the intermetallic compound ErRuSi have been investigated. The compound shows ferromagnetic ordering with Curie temperature of 8 K. The magnetic transition is found to be first order in nature. The maximum entropy change and refrigerant capacity are found to be 21.2 J/kg K and 416 J/kg for a field change of 50 kOe. The low field (20 kOe) entropy change is also found to be quite large (15.2 J/kg K). Additionally, the compound shows very little thermal and field hysteresis, fulfilling the required condition for a good magnetic refrigerant in the low temperature regime.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Cc Other ferromagnetic metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
65.40.gd Entropy
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Microscopic magnetic structuring of a spin-wave waveguide by ion implantation in a Ni81Fe19 layer

Björn Obry, Thomas Meyer, Philipp Pirro, Thomas Brächer, Bert Lägel, Julia Osten, Thomas Strache, Jürgen Fassbender, and Burkard Hillebrands

Appl. Phys. Lett. 102, 022409 (2013); http://dx.doi.org/10.1063/1.4775759 (4 pages)

Online Publication Date: 15 January 2013

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We investigate the spin-wave excitation in microscopic waveguides fabricated by localized Cr+ ion implantation in a ferromagnetic Ni81Fe19 film. We demonstrate that spin-wave waveguides can be conveniently made by this technique. The magnetic patterning technique yields an increased damping and a reduction in saturation magnetization in the implanted regions that can be extracted from Brillouin light scattering measurements of the spin-wave excitation spectra. Furthermore, the waveguide performance as well as the internal field of the waveguide depend on the doping fluence. The results prove that localized ion implantation is a powerful tool for the patterning of magnon spintronic devices.
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75.70.Ak Magnetic properties of monolayers and thin films
78.35.+c Brillouin and Rayleigh scattering; other light scattering
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.30.Ds Spin waves
75.50.Bb Fe and its alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Structurally manipulating electron-spin polarization via δ-doping in a magnetic nanostructure

Mao-Wang Lu, Zhi-Yong Wang, Yu-Li Liang, Yan-Bo An, and Li-Qiong Li

Appl. Phys. Lett. 102, 022410 (2013); http://dx.doi.org/10.1063/1.4775761 (5 pages) | Cited 1 time

Online Publication Date: 15 January 2013

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We theoretically investigate the control of the electron-spin polarization in a spin filter by a tunalbe δ-doping, where the device and the δ-doping can be realized experimentally by depositing a ferromagnetic stripe on top of semiconductor heterostructure and using molecular beam epitaxy or metal-organic chemical-vapor deposition, respectively. The δ-doping dependent transmission and conductance are numerically calculated for InAs material system. It is shown that both amplitude and sign of electron-spin polarization vary dramatically with the weight and/or the location of the δ-doping. Thus, it is possible to open a new door for effectively manipulating spin-polarized source, and the considered nanostructure can serve as a spin filter with a structurally controllable spin polarization by the δ-doping.
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75.76.+j Spin transport effects
72.25.-b Spin polarized transport
75.50.Pp Magnetic semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.uj III-V and II-VI semiconductors
75.75.-c Magnetic properties of nanostructures

Electromigration induced fast L10 ordering phase transition in perpendicular FePt films

Chun Feng, Xujing Li, Meiyin Yang, Kui Gong, Yuanmin Zhu, Qian Zhan, Li Sun, Baohe Li, Yong Jiang, and Guanghua Yu

Appl. Phys. Lett. 102, 022411 (2013); http://dx.doi.org/10.1063/1.4775692 (4 pages) | Cited 1 time

Online Publication Date: 16 January 2013

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Realizing fast L10 ordering phase transition (LOPT) in L10 structured magnetic materials without heat treatment is crucial for their applications in spintronic devices. This article reports on the electromigration controlled momentum transfer and rapid ordering of Fe and Pt atoms in the as-deposited FePt films. Lattice defects in the films provide enough diffusion pathways and allow the Fe and Pt atoms rearranging. Through the current driven atomic motion and rearrangement, fast LOPT can result in the establishment of perpendicular magnetic anisotropy of the FePt films at room temperature. This effect is expected to work with other L10 typed magnetic materials for spintronic devices development.
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66.30.Qa Electromigration
75.30.Gw Magnetic anisotropy
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Ak Magnetic properties of monolayers and thin films
64.70.kd Metals and alloys

Effect of mechanical strain on magnetic properties of flexible exchange biased FeGa/IrMn heterostructures

Xiaoshan Zhang, Qingfeng Zhan, Guohong Dai, Yiwei Liu, Zhenghu Zuo, Huali Yang, Bin Chen, and Run-Wei Li

Appl. Phys. Lett. 102, 022412 (2013); http://dx.doi.org/10.1063/1.4776661 (5 pages)

Online Publication Date: 16 January 2013

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We have fabricated flexible exchange biased heterostructures with magnetostrictive Fe81Ga19 alloy as the ferromagnetic layer and Ir20Mn80 as the antiferromagnetic layer on polyethylene terephthalate substrates. The mechanical strain can modify both the strength and the orientation of the uniaxial anisotropy, giving rise to the switching between the easy and hard magnetization directions. Different from the previously reported works on rigid exchange biased systems, a drastic decrease in exchange bias field was observed under a compressive strain with magnetic field parallel to the pinning direction, but only a slightly decrease was shown under a tensile strain. Based on a Stoner-Wohlfarth model calculation, we suggested that the distributions of both ferromagnetic and antiferromagnetic anisotropies be the key to induce the mechanically tunable exchange bias.
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75.80.+q Magnetomechanical effects, magnetostriction
75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy
75.50.Bb Fe and its alloys
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Detection of Dynabeads using a micro-electro-mechanical-systems fluxgate sensor

Jian Lei, Tao Wang, Chong Lei, and Yong Zhou

Appl. Phys. Lett. 102, 022413 (2013); http://dx.doi.org/10.1063/1.4776665 (4 pages)

Online Publication Date: 16 January 2013

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This paper presents an approach to detect the presence of Dynabeads with a system based on a micro fluxgate sensor fabricated by micro-electro-mechanical systems technology. Due to the excellent performance of the micro fluxgate sensor, the detection system exhibited many advantages, such as lower minimum detectable limit, small weight, and low power consumption. Experimental results show that, applied an external magnetic field in a range of 430 μT to 600 μT, Dynabeads with a concentration as low as 0.1 μg/ml can be detected by this system. Moreover, the detection system could give an approximate quantitation to the magnetic beads.
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07.55.Ge Magnetometers for magnetic field measurements
75.50.Tt Fine-particle systems; nanocrystalline materials
07.10.Cm Micromechanical devices and systems

Influence of Ga doping on the Cr valence state and ferromagnetism in Cr: ZnO films

Ze Xiong, Xue-Chao Liu, Shi-Yi Zhuo, Jian-Hua Yang, Er-Wei Shi, Wen-Sheng Yan, Shu-De Yao, and Hui-Ping Pan

Appl. Phys. Lett. 102, 022414 (2013); http://dx.doi.org/10.1063/1.4776689 (4 pages)

Online Publication Date: 16 January 2013

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The Zn0.97−xCr0.03GaxO (0 ≤ x ≤ 0.03) films have been prepared by inductively coupled plasma enhanced physical vapor deposition and investigated by soft x-ray absorption spectroscopy. The soft x-ray absorption spectroscopy results indicate Ga doping can substantially transform Cr3+ to Cr2+ and improve the average magnetic moment of Cr ions. The strong localization of carriers suggests the bound magnetic polarons scenario, wherein the reduced localization radius of variable range hopping by the enhancement of high valence state Cr ions can suppress the hopping probability of carriers and stabilize the bound magnetic polarons, leading to a monotonic increase in saturation magnetization.
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61.72.uj III-V and II-VI semiconductors
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films

Magnetization reversal in Nd-Fe-B based nanocomposites as seen by magnetic small-angle neutron scattering

Jens-Peter Bick, Dirk Honecker, Frank Döbrich, Kiyonori Suzuki, Elliot P. Gilbert, Henrich Frielinghaus, Joachim Kohlbrecher, Jorge Gavilano, Edward M. Forgan, Ralf Schweins, Peter Lindner, Rainer Birringer, and Andreas Michels

Appl. Phys. Lett. 102, 022415 (2013); http://dx.doi.org/10.1063/1.4776708 (5 pages)

Online Publication Date: 16 January 2013

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We have studied the magnetization-reversal process of a Nd2Fe14B/Fe3B nanocomposite using small-angle neutron scattering. Based on the computation of the autocorrelation function of the spin misalignment, we have estimated the characteristic size lC of spin inhomogeneities around the Nd2Fe14B nanoparticles. The quantity lC approaches a constant value of about 12.5 nm ( ∼ average Nd2Fe14B particle radius) at 14 T and takes on a maximum value of about 18.5 nm at the coercive field of −0.55 T. The field dependence of lC can be described by a model that takes into account the convolution relationship between the nuclear and the magnetic microstructure.
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75.75.-c Magnetic properties of nanostructures
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Jk Magnetization reversal mechanisms

Temperature and Co thickness dependent sign change of the anomalous Hall effect in Co/Pd multilayers: An experimental and theoretical study

V. Keskin, B. Aktaş, J. Schmalhorst, G. Reiss, H. Zhang, J. Weischenberg, and Y. Mokrousov

Appl. Phys. Lett. 102, 022416 (2013); http://dx.doi.org/10.1063/1.4776737 (5 pages)

Online Publication Date: 16 January 2013

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The anomalous Hall effect in ultra-thin {Co0.3 nm/Pd0.5 nm}n multilayers has been investigated recently with respect to surface and interface contributions [Guo et al., Phys. Rev. B 86, 104433 (2012)]. In this work, we observe a Co thickness and temperature dependent sign change also for {Co0.20–0.55 nm/Pd1.5nm or 1.8 nm}9x multilayers, e.g., in layer stacks with considerably thicker Pd layers and hence lower resistivity. The thickness dependent behavior can be reproduced by ab initio calculations of the Hall conductivity, for which only interfacial and bulk contributions play a role.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Tip-induced artifacts in magnetic force microscopy images

Óscar Iglesias-Freire, Jeffrey R. Bates, Yoichi Miyahara, Agustina Asenjo, and Peter H. Grütter

Appl. Phys. Lett. 102, 022417 (2013); http://dx.doi.org/10.1063/1.4776669 (4 pages)

Online Publication Date: 17 January 2013

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Useful sample information can be extracted from the dissipation in frequency modulation atomic force microscopy due to its correlation to important material properties. It has been recently shown that artifacts can often be observed in the dissipation channel, due to the spurious mechanical resonances of the atomic force microscope instrument when the oscillation frequency of the force sensor changes. In this paper, we present another source of instrumental artifacts specific to magnetic force microscopy (MFM), which is attributed to a magnetization switching happening at the apex of MFM tips. These artifacts can cause a misinterpretation of the domain structure in MFM images of magnetic samples.
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07.79.Pk Magnetic force microscopes
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.78.Fg Dynamics of domain structures
07.79.Lh Atomic force microscopes

Optimized cobalt nanowires for domain wall manipulation imaged by in situ Lorentz microscopy

L. A. Rodríguez, C. Magén, E. Snoeck, L. Serrano-Ramón, C. Gatel, R. Córdoba, E. Martínez-Vecino, L. Torres, J. M. De Teresa, and M. R. Ibarra

Appl. Phys. Lett. 102, 022418 (2013); http://dx.doi.org/10.1063/1.4776709 (5 pages)

Online Publication Date: 17 January 2013

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Direct observation of domain wall (DW) nucleation and propagation in focused electron beam induced deposited Co nanowires as a function of their dimensions was carried out by Lorentz microscopy (LTEM) upon in situ application of magnetic field. Optimal dimensions favoring the unambiguous DW nucleation/propagation required for applications were found in 500-nm-wide and 13-nm-thick Co nanowires, with a maximum nucleation field and the largest gap between nucleation and propagation fields. The internal DW structures were resolved using the transport-of-intensity equation formalism in LTEM images and showed that the optimal nanowire dimensions correspond to the crossover between the nucleation of transverse and vortex walls.
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75.60.Ch Domain walls and domain structure
81.15.Jj Ion and electron beam-assisted deposition; ion plating
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)
75.75.-c Magnetic properties of nanostructures
81.07.Gf Nanowires
75.50.Tt Fine-particle systems; nanocrystalline materials

Combinatorial exploration of rare-earth-free permanent magnets: Magnetic and microstructural properties of Fe-Co-W thin films

T. R. Gao, Y. Q. Wu, S. Fackler, I. Kierzewski, Y. Zhang, A. Mehta, M. J. Kramer, and I. Takeuchi

Appl. Phys. Lett. 102, 022419 (2013); http://dx.doi.org/10.1063/1.4775581 (4 pages)

Online Publication Date: 18 January 2013

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We have investigated the magnetic and structural properties of Fe-Co-W films using a composition spread technique. From the magnetometry measurements, large magnetization (900  emu/cm3) and enhanced perpendicular coercive fields (2–3 kOe) of low W concentration films were observed. The synchrotron diffraction results show a structural transition from a crystalline to an amorphous state and the crystallization onset increases with increasing W concentration. The SEM and TEM characterizations show that the films with low W concentrations have vertically standing platelet-like grain structures which is ascribed to the enhanced coercive fields. Magnetometry studies indicate that as the W concentration increases, microstructural change results in evolution of magnetization reversal mechanism.
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75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.50.Vv High coercivity materials
75.50.Ww Permanent magnets
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Jk Magnetization reversal mechanisms

Spin lifetime measurements in GaAsBi thin films

Brennan Pursley, M. Luengo-Kovac, G. Vardar, R. S. Goldman, and V. Sih

Appl. Phys. Lett. 102, 022420 (2013); http://dx.doi.org/10.1063/1.4781415 (4 pages)

Online Publication Date: 18 January 2013

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Photoluminescence spectroscopy and Hanle effect measurements are used to investigate carrier spin dephasing and recombination times in the semiconductor alloy GaAsBi as a function of temperature and excitation energy. Hanle effect measurements reveal the product of g-factor and effective spin dephasing time (gTs) ranges from 0.8 ns at 40 K to 0.1 ns at 120 K. The temperature dependence of gTs provides evidence for a thermally activated effect, which is attributed to hole localization at single Bi or Bi cluster sites below 40 K.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.55.Cr III-V semiconductors
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Giant magnetocaloric effect in Ho12Co7 compound

X. Q. Zheng, X. P. Shao, J. Chen, Z. Y. Xu, F. X. Hu, J. R. Sun, and B. G. Shen

Appl. Phys. Lett. 102, 022421 (2013); http://dx.doi.org/10.1063/1.4788706 (5 pages)

Online Publication Date: 18 January 2013

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Magnetic properties and magnetocaloric effects of Ho12Co7 compound are investigated by magnetization and heat capacity measurement. The Ho12Co7 compound undergoes antiferromagnetic (AFM)-AFM transition at T1 = 9 K, AFM-ferromagnetic (FM) transition at T2 = 17 K, and FM-paramagnetic transition at TC = 30 K, with temperature increasing. There are two peaks on the magnetic entropy change (ΔSM) versus temperature curves and the maximal value of –ΔSM is found to be 19.2 J/kg K with the refrigerant capacity value of 554.4 J/kg under a field change from 0 to 5 T. The shape of the ΔSM-T curves obtained from heat capacity measurement is in accordance with that from magnetization measurement. The excellent magnetocaloric performance indicates the applicability of Ho12Co7 as an appropriate candidate for magnetic refrigerant in low temperature ranges.
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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.)

d0 magnetism in semiconductors through confining delocalized atomic orbitals

E. J. Kan, Fang Wu, Haiping Wu, Chuanyun Xiao, Hongjun Xiang, and Kaiming Deng

Appl. Phys. Lett. 102, 022422 (2013); http://dx.doi.org/10.1063/1.4788726 (3 pages)

Online Publication Date: 18 January 2013

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Although localized atomic 2p orbitals have been taken as the possible origin of d0 materials, the collective magnetic ordering is impeded by the low concentration of local magnetic moments. Using first-principles calculations with wurtzite GaN as a prototype material, we predict that the delocalized defect orbitals can induce local magnetic moments and form collective magnetic ordering through confinement. By applying external strain, the delocalized defect orbitals which are partially filled by anion-vacancy are well confined, leading to the spontaneous spin ordering.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Pp Magnetic semiconductors
61.72.jd Vacancies
72.25.-b Spin polarized transport

Influence of the dynamic lattice strain on the transport behavior of oxide heterojunctions

J. Wang, F. X. Hu, L. Chen, Y. Y. Zhao, H. X. Lu, J. R. Sun, and B. G. Shen

Appl. Phys. Lett. 102, 022423 (2013); http://dx.doi.org/10.1063/1.4788731 (5 pages)

Online Publication Date: 18 January 2013

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All-perovskite oxide heterojunctions composed of electron-doped titanate LaxSr1 − xTiO3 (x = 0.1, 0.15) and hole-doped manganite La0.67Ca0.33MnO3 films were fabricated on piezoelectric substrate of (001)-0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT). Taking advantage of the excellent converse piezoelectric effect of PMN-PT, we investigated the influence of the dynamic lattice strain on transport properties of the heterojunctions by applying external bias electric fields on the PMN-PT substrate. Photovoltaic experiments were carried out to characterize the interfacial barrier of the heterojunction. A linear reduction in the barrier height was observed with the increase of the bias field applied on PMN-PT. The value of the barrier height reduces from ∼1.55 (∼1.30) to 1.02 (1.08) eV as the bias field increases from 0 to 12 kV/cm for the junction of La0.10Sr0.9TiO3/La0.67Ca0.33MnO3 (La0.15Sr0.85TiO3/La0.67Ca0.33MnO3). The observed dependency of barrier height on external field can be ascribed to the increasing release of trapped carriers by strain modulation, which results in a suppression of the depletion layer and increases the opportunity for electron tunneling across the depletion area.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Pz Photoconduction and photovoltaic effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.40.Gk Tunneling

Tunable topological electronic structures in Sb(111) bilayers: A first-principles study

Feng-Chuan Chuang, Chia-Hsiu Hsu, Chia-Yu Chen, Zhi-Quan Huang, Vidvuds Ozolins, Hsin Lin, and Arun Bansil

Appl. Phys. Lett. 102, 022424 (2013); http://dx.doi.org/10.1063/1.4776734 (4 pages)

Online Publication Date: 18 January 2013

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Electronic structures and band topology of a single Sb(111) bilayer in the buckled honeycomb configuration are investigated using first-principles calculations. A nontrivial topological insulating phase can be induced by tensile strain, indicating the possibility of realizing the quantum spin Hall state for Sb thin films on suitable substrates. The presence of buckling provides an advantage in controlling the band gap through an out-of-plane external electric field, making a topological phase transition with six spin-polarized Dirac cones at the critical point. With a tunable gap and reversible spin polarization, Sb thin films are promising candidates for spintronic applications.
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71.20.Ps Other inorganic compounds
72.25.-b Spin polarized transport
73.61.Ng Insulators
81.40.Lm Deformation, plasticity, and creep
62.20.mq Buckling
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
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Nanosecond voltage pulses from dendritic flux avalanches in superconducting NbN films

P. Mikheenko, A. J. Qviller, J. I. Vestgården, S. Chaudhuri, I. J. Maasilta, Y. M. Galperin, and T. H. Johansen

Appl. Phys. Lett. 102, 022601 (2013); http://dx.doi.org/10.1063/1.4775693 (3 pages)

Online Publication Date: 15 January 2013

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Combined voltage and magneto-optical study of magnetic flux flow in superconducting NbN films is reported. The nanosecond-scale voltage pulses appearing during thermomagnetic avalanches have been recorded in films partially coated by a metal layer. Simultaneous magneto-optical imaging and voltage measurements allowed the pulses to be associated with individual flux branches penetrating the superconductor below the metal coating. From detailed characteristics of pulse and flux branches, the electrical field in the superconductor is found to be in the range of 5-50 kV/m, while the propagation speed of the avalanche during its final stage is found to be close to 5 km/s.
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74.78.-w Superconducting films and low-dimensional structures
78.20.Ls Magneto-optical effects
74.25.Wx Vortex pinning (includes mechanisms and flux creep)
74.25.fg Thermoelectric effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
74.25.Gz Optical properties
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Interfacial bonding and electronic structure of HfO2/GaSb interfaces: A first principles study

K. Xiong, W. Wang, D. M. Zhernokletov, Santosh K. C., R. C. Longo, R. M. Wallace, and K. Cho

Appl. Phys. Lett. 102, 022901 (2013); http://dx.doi.org/10.1063/1.4775665 (5 pages) | Cited 1 time

Online Publication Date: 15 January 2013

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The interfacial bonding and electronic structure of HfO2/GaSb interfaces has been investigated through first principles calculations. The calculated electronic structures of these interfaces reveal that some O-rich interfaces are semiconducting interfaces without any gap states. In contrast, for the interfaces with lower interfacial O content, gap states appear in the GaSb band gap, close to the conduction band. The valence band offsets are found to vary from 2.2 eV to 3.6 eV, depending on the interfacial O content. Our results suggest that GaSb is a suitable material to form high quality interface with HfO2.
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73.20.At Surface states, band structure, electron density of states
71.15.-m Methods of electronic structure calculations
71.20.Nr Semiconductor compounds

Memory diodes with nonzero crossing

Shimon Saraf, Miri Markovich, Tracey Vincent, Roman Rechter, and Avner Rothschild

Appl. Phys. Lett. 102, 022902 (2013); http://dx.doi.org/10.1063/1.4775673 (4 pages) | Cited 1 time

Online Publication Date: 15 January 2013

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Memristors combine switching, memory, and rectification functions in two-terminal nanoelectronic devices. The theory says that their current-voltage (I-V) characteristics cross over at the zero crossing point (I = V = 0), and the results reported hitherto conform to this theorem. Here, we extend the family of memristive devices, adding memory diodes (memdiodes) comprising SrTiO3 pn junctions that display unique combination of rectification, hysteresis, and nonzero crossing. Reverse bias polarization gives rise to a nonzero open circuit voltage that persists after the junction is disconnected from the external circuit. This opens up an opportunity for a new type of nonvolatile memories.
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84.30.Sk Pulse and digital circuits
84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
85.30.Kk Junction diodes

Relaxor behavior of ferroelectric Ca0.22Sr0.12Ba0.66Nb2O6

Chandra Shekhar Pandey, Jürgen Schreuer, Manfred Burianek, and Manfred Mühlberg

Appl. Phys. Lett. 102, 022903 (2013); http://dx.doi.org/10.1063/1.4775686 (4 pages)

Online Publication Date: 15 January 2013

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The relaxor behavior of tetragonal tungsten bronze uniaxial relaxor ferroelectric calcium strontium barium niobate (Ca0.22Sr0.12Ba0.66Nb2O6 or CSBN-22) single crystal was studied by measuring elastic constants and thermal expansion with the aid of resonant ultrasound spectroscopy and dilatometry, respectively, in the temperature range 300 K–1503 K. Thermal expansion yields evidence of the Burns temperature TB and the intermediate characteristic temperature T*, which was also supported by the temperature evolutions of the elastic constants cij. CSBN-22 was found to be ∼2%–3% elastically stiffer than CBN-28. The presented results open the perspective to understand the relaxor behavior of CSBN.
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77.80.B- Phase transitions and Curie point
77.80.Jk Relaxor ferroelectrics
77.84.Ek Niobates and tantalates
65.40.De Thermal expansion; thermomechanical effects
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.dq Other elastic constants

Improving dielectric properties of epitaxial Gd2O3 thin films on silicon by nitrogen doping

Ayan Roy Chaudhuri, A. Fissel, V. R. Archakam, and H. J. Osten

Appl. Phys. Lett. 102, 022904 (2013); http://dx.doi.org/10.1063/1.4775688 (4 pages) | Cited 1 time

Online Publication Date: 15 January 2013

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We report about the effect of nitrogen doping on the electrical properties of epitaxial Gd2O3 thin films. Epitaxial Gd2O3:N thin films were grown on Si (111) substrates by solid source molecular beam epitaxy using nitrous oxide as the nitridation agent. Substitutional nitrogen incorporation into the dielectric layer was confirmed by secondary ion mass spectroscopy and X-ray photoelectron spectroscopy analysis. Substantial reduction of the leakage current density and disappearance of hysteresis in capacitance-voltage characteristics observed in the Gd2O3:N layers indicate that nitrogen incorporation in Gd2O3 effectively eliminates the adverse effects of the oxygen vacancy induced defects in the oxide layer.
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77.55.Px Epitaxial and superlattice films
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Ng Insulators
77.22.Ch Permittivity (dielectric function)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.up Other materials

Enhanced piezoelectric and ferroelectric properties in the BaZrO3 substituted BiFeO3-PbTiO3

Longlong Fan, Jun Chen, Sha Li, Huajun Kang, Laijun Liu, Liang Fang, and Xianran Xing

Appl. Phys. Lett. 102, 022905 (2013); http://dx.doi.org/10.1063/1.4775763 (5 pages)

Online Publication Date: 15 January 2013

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BiFeO3-PbTiO3 (BF-PT) compounds possess very high Curie temperature and tetragonality compared to other PbTiO3-based piezoceramics. The BaZrO3 (BZ), with weakly ferroelectric active cations, was introduced into the BiFeO3-PbTiO3 to reduce the tetragonality (c/a) and improve the piezoelectric property. For the (0.8-x)BiFeO3-0.2BaZrO3-xPbTiO3, the BaZrO3 substitution can effectively decrease the tetragonality (c/a) from 1.18 to 1.02 for those compositions near the morphotropic phase boundary. The piezoelectric property of BiFeO3-PbTiO3 can be much enhanced with an optimal piezoelectric constant ∼270 pC/N with a reduced TC of 270 °C. Both the temperature dependent dielectric properties and polarization loops verified the existence of antiferroelectric relaxor, which was not observed in previous reported BiFeO3-PbTiO3 based materials.
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77.65.Bn Piezoelectric and electrostrictive constants
77.80.-e Ferroelectricity and antiferroelectricity
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization

Magnetoelectric coupling in Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 thin films deposited on Pt/TiO2/SiO2/Si substrate

C. Cibert, J. Zhu, G. Poullain, R. Bouregba, J. More-Chevalier, and A. Pautrat

Appl. Phys. Lett. 102, 022906 (2013); http://dx.doi.org/10.1063/1.4775764 (4 pages)

Online Publication Date: 15 January 2013

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Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 (Terfenol-D/Pt/PZT) thin films were sputtered on Pt/TiO2/SiO2/Si substrate. PZT and Terfenol-D layers were chosen for their large piezoelectric and magnetostrictive coefficients, respectively. 4%–5% magnetocapacitance has been measured on a Terfenol-D/Pt/PZT stack at room temperature. A magnetoelectric (ME) voltage coefficient of 150 mV/cm Oe was obtained at low dc magnetic field out of mechanical resonance. This work demonstrates the possibility to achieve ME effect in integrated devices involving Terfenol-D and PZT thin films providing that the diffusion, which may occur between both active layers is reduced using an intermediate layer.
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77.55.Nv Multiferroic/magnetoelectric films
77.55.hn Other piezoelectric or electrostrictive films
75.80.+q Magnetomechanical effects, magnetostriction
81.15.Cd Deposition by sputtering
85.70.Ec Magnetostrictive, magnetoacoustic, and magnetostatic devices
75.85.+t Magnetoelectric effects, multiferroics

Nitrogen-passivated dielectric/InGaAs interfaces with sub-nm equivalent oxide thickness and low interface trap densities

Varistha Chobpattana, Junwoo Son, Jeremy J. M. Law, Roman Engel-Herbert, Cheng-Ying Huang, and Susanne Stemmer

Appl. Phys. Lett. 102, 022907 (2013); http://dx.doi.org/10.1063/1.4776656 (3 pages)

Online Publication Date: 15 January 2013

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We report on the electrical characteristics of HfO2 and HfO2/Al2O3 gate dielectrics deposited on n-In0.53Ga0.47As by atomic layer deposition, after in-situ hydrogen or nitrogen plasma surface cleaning procedures, respectively. It is shown that alternating cycles of nitrogen plasma and trimethylaluminum prior to growth allow for highly scaled dielectrics with equivalent oxide thicknesses down to 0.6 nm and interface trap densities that are below 2.5 × 1012 cm−2 eV−1 near midgap. It is shown that the benefits of the nitrogen plasma surface cleaning procedure are independent of the specific dielectric.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation
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