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27 Feb 2012

Volume 100, Issue 9, Articles (09xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 093101 (2012); http://dx.doi.org/10.1063/1.3687190 (4 pages)

Jinhai Mao, Li Huang, Yi Pan, Min Gao, Junfeng He, Haitao Zhou, Haiming Guo, Yuan Tian, Qiang Zou, Lizhi Zhang, Haigang Zhang, Yeliang Wang, Shixuan Du, Xingjiang Zhou, A. H. Castro Neto, et al.
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Exciton spin relaxation in In0.53Ga0.47As/AlAs0.56Sb0.44 quantum wells

K. Sasayama, S. Nakanishi, R. Yamaguchi, Y. Oyanagi, T. Ushimi, S. Gozu, T. Mozume, and A. Tackeuchi

Appl. Phys. Lett. 100, 092401 (2012); http://dx.doi.org/10.1063/1.3690833 (3 pages)

Online Publication Date: 29 February 2012

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The spin relaxation process of In0.53Ga0.47As/AlAs0.56Sb0.44 quantum wells is investigated by spin-dependent pump and probe reflectance measurements with a high time resolution of 200 fs. The observed spin relaxation time of 17.5 ps at 20 K indicates high potential for applications to high-speed optical devices. A positive temperature dependence of the spin relaxation time due to the unique band structure is observed at 30–100 K. The spin relaxation is found to be mainly governed by the Bir-Aronov-Pikus process [Sov. Phys. JETP 42, 705 (1976)] below 100 K and by the D’yakonov-Perel’ process above 100 K.
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71.35.-y Excitons and related phenomena
73.20.At Surface states, band structure, electron density of states
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.67.De Quantum wells
71.20.Nr Semiconductor compounds

In situ multifrequency ferromagnetic resonance and x-ray magnetic circular dichroism investigations on Fe/GaAs(110): Enhanced g-factor

F. M. Römer, M. Möller, K. Wagner, L. Gathmann, R. Narkowicz, H. Zähres, B. R. Salles, P. Torelli, R. Meckenstock, J. Lindner, and M. Farle

Appl. Phys. Lett. 100, 092402 (2012); http://dx.doi.org/10.1063/1.3687726 (4 pages)

Online Publication Date: 1 March 2012

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We determined the magnetic anisotropy energy and g-factor of an uncapped 10 nm thick Fe/GaAs(110) film using a setup that allows frequency (1.5–26.5 GHz) as well as angular dependent ferromagnetic resonance measurements under ultrahigh vacuum conditions. The g-factor g = 2.61±0.1 is unusually high at room temperature and can be interpreted as the result of an increased orbital moment due to strain. This interpretation is supported by more surface sensitive x-ray magnetic circular dichroism measurements which yield g = 2.21±0.02 measured at remanence. The difference in g may be the result of magnetic field dependent magnetostriction which influences the orbital moment.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
72.30.+q High-frequency effects; plasma effects
75.30.Gw Magnetic anisotropy
78.20.Ls Magneto-optical effects
78.66.-w Optical properties of specific thin films
75.80.+q Magnetomechanical effects, magnetostriction

Enhanced spin pumping at yttrium iron garnet/Au interfaces

C. Burrowes, B. Heinrich, B. Kardasz, E. A. Montoya, E. Girt, Yiyan Sun, Young-Yeal Song, and Mingzhong Wu

Appl. Phys. Lett. 100, 092403 (2012); http://dx.doi.org/10.1063/1.3690918 (4 pages) | Cited 11 times

Online Publication Date: 1 March 2012

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Spin injection across the ferrimagnetic insulator yttrium iron garnet (YIG)/normal metal Au interface was studied using ferromagnetic resonance. The spin mixing conductance was determined by comparing the Gilbert damping parameter α in YIG/Au and YIG/Au/Fe heterostructures. The main purpose of this study was to correlate the spin pumping efficiency with chemical modifications of the YIG film surface using in situ etching and deposition techniques. By means of Ar+ ion beam etching, one is able to increase the spin mixing conductance at the YIG/Au interface by a factor of 5 compared to the untreated YIG/Au interface.
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72.25.Mk Spin transport through interfaces
73.40.Ns Metal-nonmetal contacts
75.50.Dd Nonmetallic ferromagnetic materials
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Room-temperature anomalous Hall effect in amorphous Si-based magnetic semiconductor

Jia-Hsien Yao, Hsiu-Hau Lin, Yun-Liang Soo, Tai-Sing Wu, Jai-Lin Tsai, Ming-Der Lan, and Tsung-Shune Chin

Appl. Phys. Lett. 100, 092404 (2012); http://dx.doi.org/10.1063/1.3691173 (4 pages) | Cited 1 time

Online Publication Date: 1 March 2012

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Here, we show that Mn-doped amorphous hydrogenated Si reveals room-temperature ferromagnetism. Various characterization techniques rule out the formation of magnetic clusters. In particular, anomalous Hall-effect is found even at 300 K in annealed Si89.5Mn10.5 samples. The observed anomalous Hall-effect provides direct evidence that the ferromagnetic order is coupled to the itinerant carriers, making these samples workable magnetic semiconductors. This work demonstrates the great potential for Si-based semiconductor spintronics at room temperature, which is readily integrated with the current information technology.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.80.Cw Elemental semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
61.72.Cc Kinetics of defect formation and annealing

Nonuniform current and spin accumulation in a 1 μm thick n-GaAs channel

B. Endres, M. Ciorga, R. Wagner, S. Ringer, M. Utz, D. Bougeard, D. Weiss, C. H. Back, and G. Bayreuther

Appl. Phys. Lett. 100, 092405 (2012); http://dx.doi.org/10.1063/1.3691175 (4 pages)

Online Publication Date: 1 March 2012

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The spin accumulation in a n-GaAs channel produced by spin extraction into a (Ga,Mn)As contact is measured by cross-sectional imaging of the spin polarization in GaAs. The spin polarization is observed in a 1 μm thick n-GaAs channel with the maximum polarization near the contact edge opposite to the maximum current density. The one-dimensional model of electron drift and spin diffusion, frequently used, cannot explain this observation. It also leads to incorrect spin lifetimes from Hanle curves with a strong bias and distance dependence. Numerical simulations based on a two-dimensional drift-diffusion model, however, reproduce the observed spin distribution quite well and lead to realistic spin lifetimes.
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72.25.Dc Spin polarized transport in semiconductors
75.30.Ds Spin waves
75.30.Wx Spin crossover
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.50.Pp Magnetic semiconductors
75.78.Cd Micromagnetic simulations

Physical limits of pure superparamagnetic Fe3O4 nanoparticles for a local hyperthermia agent in nanomedicine

Minhong Jeun, Sanghoon Lee, Jae Kyeong Kang, Asahi Tomitaka, Keon Wook Kang, Young Il Kim, Yasushi Takemura, Kyung-Won Chung, Jiyeon Kwak, and Seongtae Bae

Appl. Phys. Lett. 100, 092406 (2012); http://dx.doi.org/10.1063/1.3689751 (4 pages) | Cited 2 times

Online Publication Date: 1 March 2012

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Magnetic and AC magnetically induced heating characteristics of Fe3O4 nanoparticles (IONs) with different mean diameters, d, systematically controlled from 4.2 to 22.5 nm were investigated to explore the physical relationship between magnetic phase and specific loss power (SLP) for hyperthermia agent applications. It was experimentally confirmed that the IONs had three magnetic phases and correspondingly different SLP characteristics depending on the particle sizes. Furthermore, it was demonstrated that pure superparamagnetic phase IONs (d < 9.8 nm) showed insufficient SLPs critically limiting for hyperthermia applications due to smaller AC hysteresis loss power (Néel relaxation loss power) originated from lower out-of-phase magnetic susceptibility.
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87.85.Rs Nanotechnologies-applications
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
87.19.Pp Biothermics and thermal processes in biology
87.85.J- Biomaterials

Half-metallic p-electron ferromagnetism in alkaline earth doped AlAs: A first-principles calculation

Yong-Hong Zhao, Yong-Feng Li, and Yong Liu

Appl. Phys. Lett. 100, 092407 (2012); http://dx.doi.org/10.1063/1.3692591 (3 pages) | Cited 1 time

Online Publication Date: 2 March 2012

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We investigated the p-electron ferromagnetism in alkaline earth doped AlAs by using first-principles calculations. The modified Becke and Johnson potential is used to give a much more reasonable semiconductor gap. Our results demonstrate that ferromagnetic phase is always energetically favorable than the antiferromagnetic and nonmagnetic ones for all considered compounds. Magnetic moments are mainly attributed to the partly filled anionic p states. Especially, half-metallic ferromagnetism has been obtained for Ca- and Sr-doped AlAs, which may be promising for spintronic applications. The calculated results are also useful for understanding of the origin of ferromagnetism in diluted magnetic semiconductors.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Pp Magnetic semiconductors
75.50.Ee Antiferromagnetics
71.55.Eq III-V semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
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