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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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Influence of organic layer thickness on structure, magnetic, and transport properties of Langmuir-Blodgett ttb-CuPc/CoFe

T. Yu, Q. T. Zhang, D. P. Liu, and X. F. Han

Appl. Phys. Lett. 102, 022401 (2013); http://dx.doi.org/10.1063/1.4775590 (3 pages)

Online Publication Date: 14 January 2013

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In this letter, the ill-defined layer in organic/metal vertical structure was examined using ttb-CuPc/CoFe films. The ill-defined layer thickness was estimated. Beside the usually observed damages to organic underlayer, it is found that ill-defined layer may also influence film properties by modulating the growth of top metal layer. In our case, granular rather than continuous CoFe film was found as increasing ttb-CuPc underlayer thickness with a corresponding change in film's magnetic and transport properties.
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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.)
72.25.-b Spin polarized transport

Search for spin gapless semiconductors: The case of inverse Heusler compounds

S. Skaftouros, K. Özdoğan, E. Şaşıoğlu, and I. Galanakis

Appl. Phys. Lett. 102, 022402 (2013); http://dx.doi.org/10.1063/1.4775599 (4 pages) | Cited 3 times

Online Publication Date: 14 January 2013

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We employ ab-initio electronic structure calculations to search for spin gapless semiconductors among the inverse Heusler compounds. The occurrence of this property is not accompanied by a general rule and results are materials specific. The six compounds identified show semiconducting behavior concerning the spin-down band structure and in the spin-up band structure the valence and conduction bands touch each other leading to 100% spin-polarized carriers. Moreover, these six compounds should exhibit also high Curie temperatures and thus are suitable for spintronics applications.
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81.05.Hd Other semiconductors
71.15.-m Methods of electronic structure calculations
71.20.Nr Semiconductor compounds
72.25.-b Spin polarized transport
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Effect of magnetic order on nucleation in undercooled Co80Pd20 melts

Shengyin Zhou, Rui Hu, Jinshan Li, Hui Chang, Hongchao Kou, and Lian Zhou

Appl. Phys. Lett. 102, 022403 (2013); http://dx.doi.org/10.1063/1.4775676 (3 pages)

Online Publication Date: 14 January 2013

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Co80Pd20 melts have been undercooled below Curie temperature of the liquids (TCL) by employing the method of molten glass denucleation combined with cyclic superheating. The largest undercooling achieved is 465 K, which indicates that the nucleation temperature is below TCL more than 100 K and then the ferromagnetic liquid is obtained. The nucleation behavior is analyzed using the classical nucleation theory extended by magnetic contributions to the Gibbs free energy. The results reveal that the onset of magnetic order facilitates rather than stimulates nucleation. Consequently, Co80Pd20 melts can be undercooled below TCL.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Cc Other ferromagnetic metals and alloys
75.50.Mm Magnetic liquids
75.50.Tt Fine-particle systems; nanocrystalline materials
64.60.Q- Nucleation
65.20.Jk Studies of thermodynamic properties of specific liquids

Half-metallic ferromagnetism in wurtzite ScM (M=C, Si, Ge, and Sn): Ab initio calculations

S. W. Fan, L. J. Ding, Z. L. Wang, and K. L. Yao

Appl. Phys. Lett. 102, 022404 (2013); http://dx.doi.org/10.1063/1.4775680 (5 pages)

Online Publication Date: 14 January 2013

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Using the full potential linearized augment plane wave method with the modified Becke and Johnson (mBJ) potential, the half-metallicity and electronic structure for the wurtzite ScM (M = C, Si, Ge, and Sn) compounds are investigated. The ScM series compounds are found to be excellent half-metallic ferromagnets (HMFs) with large half-metallic gaps (0.76–0.33 eV). The magnetic moments are 2.00 μB per cell, and p-d hybridization mechanism plays crucial role in forming the half-metallic ferromagnetism. The ferromagnetic ground states, larger half metallic gaps, the robust half-metallicity with respect to the lattice compression, negative cohesive energy, and heat of formation indicate ScM compounds would be promising HMFs.
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71.20.Nr Semiconductor compounds
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Pp Magnetic semiconductors
82.60.Cx Enthalpies of combustion, reaction, and formation
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
71.15.Nc Total energy and cohesive energy calculations

Landau-Lifshitz-Bloch-Slonczewski simulations of the spin-transfer-torque driven magnetization switching assisted by Joule heating

Eugen Oniciuc, Laurentiu Stoleriu, and Alexandru Stancu

Appl. Phys. Lett. 102, 022405 (2013); http://dx.doi.org/10.1063/1.4775682 (4 pages)

Online Publication Date: 14 January 2013

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In this paper, we show that Landau-Lifshitz-Bloch-Slonczewski equation can be envisaged as one of the best options for the modeling of heat assisted spin transfer torque writing. The model is tested on a Joule assisted switching problem for a macrospin under a polarized current, with all the values for the parameters in the typical range used technologically. The switching diagram in the presence of the current is presented, explained, and the agreement with published experimental data is discussed.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Spin pumping by nonreciprocal spin waves under local excitation

R. Iguchi, K. Ando, Z. Qiu, T. An, E. Saitoh, and T. Sato

Appl. Phys. Lett. 102, 022406 (2013); http://dx.doi.org/10.1063/1.4775685 (3 pages)

Online Publication Date: 14 January 2013

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We measured spatial distribution of spin pumping by nonreciprocal magnetostatic surface waves (MSSWs) using inverse spin Hall effect (ISHE) in a YIG/Pt system under local excitation. The local intensity of spin pumping by MSSWs shows center displacement of ± 0.1 mm from the center of a waveguide according to the reversal of a bias field, which is due to the nonreciprocal propagation of MSSWs over a macroscopic distance. The combination of spin pumping and ISHE enables electrical investigation of local spin dynamics in a magnetic insulator.
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75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Rf Surface magnetism
72.25.-b Spin polarized transport

Damping of CoxFe80−xB20 ultrathin films with perpendicular magnetic anisotropy

T. Devolder, P.-H. Ducrot, J.-P. Adam, I. Barisic, N. Vernier, Joo-Von Kim, B. Ockert, and D. Ravelosona

Appl. Phys. Lett. 102, 022407 (2013); http://dx.doi.org/10.1063/1.4775684 (4 pages)

Online Publication Date: 15 January 2013

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We use vector network analyzer ferromagnetic resonance to study the perpendicularly magnetized CoFeB films. We report the dependence of the anisotropy, the g-factor, and the damping upon the Fe-Co compositional ratio in the amorphous and crystalline states. The damping and the anisotropy increase upon crystallization but vary little with composition on the Fe-rich side. At high cobalt content, the anisotropy lowers while the damping and the sample inhomogeneity increase. The compositional dependences seem to extrapolate from the properties of bulk CoFe alloys, with differences that can be understood from the correlated impacts of spin-orbit interaction on anisotropy, g-factor, and damping.
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75.70.Ak Magnetic properties of monolayers and thin films
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.70.Tj Spin-orbit effects
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
75.30.Gw Magnetic anisotropy
75.50.Bb Fe and its alloys

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) | Cited 1 time

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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