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9 Jun 2008

Volume 92, Issue 23, Articles (23xxxx)

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Appl. Phys. Lett. 92, 231901 (2008); http://dx.doi.org/10.1063/1.2938921 (3 pages)

N. A. Mara, D. Bhattacharyya, P. Dickerson, R. G. Hoagland, and A. Misra
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Dynamics of magnetization, reversal, and ultrafast demagnetization of TbFeCo amorphous films

Xiaodong Liu, Zhen Xu, Ruixin Gao, Haining Hu, Zhifeng Chen, Zixin Wang, Jun Du, Shiming Zhou, and Tianshu Lai

Appl. Phys. Lett. 92, 232501 (2008); http://dx.doi.org/10.1063/1.2943281 (3 pages) | Cited 6 times

Online Publication Date: 11 June 2008

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Static and dynamic hysteresis loops of TbFeCo amorphous films are measured by vibrating sample magnetometry (VSM) and magneto-optical Kerr rotation. The static VSM loop shows a faster magnetization reversal than the static Kerr loop does. The dynamic Kerr hysteresis loop in a sinusoidal alternating magnetic field at 1.14 kHz shows a large increase in coercivity with respect to the static coercivity. The ultrafast dynamics of laser-induced demagnetization and magnetization recovery is studied by femtosecond time-resolved polar Kerr rotation spectroscopy, and shows a subpicosecond demagnetization and several hundreds of picosecond magnetization recovery process, which suggests gigahertz writing rate possible.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Jk Magnetization reversal mechanisms
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects
78.47.D- Time resolved spectroscopy (>1 psec)

Interesting magnetic behavior from reduced titanium dioxide nanobelts

S. V. Chong, K. Kadowaki, J. Xia, and H. Idriss

Appl. Phys. Lett. 92, 232502 (2008); http://dx.doi.org/10.1063/1.2944141 (3 pages) | Cited 6 times

Online Publication Date: 11 June 2008

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The magnetic behavior of titanium dioxide nanobelts has been investigated with and without Co doping. Room temperature ferromagnetism was observed when the Co-doped anatase TiO2 nanobelts were prepared via vacuum annealing of 2.5 at. % Co-doped titanate nanobelts, while annealing them in air resulted in paramagnetic ordering. Interestingly, by vacuum annealing the undoped titanate nanobelts under the same conditions, superparamagnetic ordering was observed in the resulting anatase TiO2 nanobelts. The electron paramagnetic resonance of this latter sample shows a strong symmetrical signal at g = 2.003 suggesting some sort of exchange interactions among the localized electrons’ spin moments from single electron trapped in oxygen vacancies.
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75.30.Et Exchange and superexchange interactions
61.72.jd Vacancies
75.30.Cr Saturation moments and magnetic susceptibilities
75.20.Ck Nonmetals
61.72.Cc Kinetics of defect formation and annealing
81.16.-c Methods of micro- and nanofabrication and processing

Nano-optics with spin waves at microwave frequencies

Vladislav E. Demidov, Sergej O. Demokritov, Karsten Rott, Patryk Krzysteczko, and Guenter Reiss

Appl. Phys. Lett. 92, 232503 (2008); http://dx.doi.org/10.1063/1.2945000 (3 pages) | Cited 42 times

Online Publication Date: 12 June 2008

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With the recent development in nanoscale patterning techniques, the potential of practical applications of nanometer-size structures for signal processing has been growing continuously. Experimental findings on the manipulation of optical signals in nanostructures have recently given rise to a widely addressed scientific area—subwavelength nano-optics. Here, we demonstrate that spin waves in microscopic ferromagnetic film structures represent a superb object for realization of the principles of nano-optics in the microwave frequency range. We show experimentally that by using the unique properties of spin waves, one can easily channelize, split, and manipulate submicrometer-width spin-wave beams propagating in microscopic magnetic-film waveguides.
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42.79.Gn Optical waveguides and couplers
84.40.-x Radiowave and microwave (including millimeter wave) technology
42.79.Wc Optical coatings
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
75.30.Ds Spin waves
81.16.Rf Micro- and nanoscale pattern formation

Impact of the electrical connection of spin transfer nano-oscillators on their synchronization: an analytical study

B. Georges, J. Grollier, V. Cros, and A. Fert

Appl. Phys. Lett. 92, 232504 (2008); http://dx.doi.org/10.1063/1.2945636 (3 pages) | Cited 17 times

Online Publication Date: 12 June 2008

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We analytically study the impact of an electrical connection of spin transfer nano-oscillators (STNOs) on their synchronization. We demonstrate that the phase dynamics of coupled STNO arrays can be described in the framework of the Kuramoto model. The conditions for successful synchronization of an assembly of STNOs are formulated. Synchronizing an assembly of STNOs appears to be the only solution to make the breakthrough on the emitted output power toward frequency synthesizers. In these potential devices, a large number of STNOs will have to be electrically connected, whatever the coupling mechanisms between oscillators.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
84.40.-x Radiowave and microwave (including millimeter wave) technology
84.30.Ng Oscillators, pulse generators, and function generators

The LaFe11.2Co0.7Si1.1Cx carbides for magnetic refrigeration close to room temperature

Mohamed Balli, Daniel Fruchart, and Damien Gignoux

Appl. Phys. Lett. 92, 232505 (2008); http://dx.doi.org/10.1063/1.2939098 (3 pages) | Cited 17 times

Online Publication Date: 13 June 2008

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The influence of carbon on the structural, magnetic, and magnetocaloric properties of LaFe11.2Co0.7Si1.1Cx compounds was investigated. The Curie temperature increases with increasing the carbon content. The maximum magnetic entropy changes under a magnetic field change of 5 T are about 14.5, 9.8, and 8.3 J/kg K for x = 0.1, 0.2, and 0.3, respectively. A composite material based on LaFe11.2Co0.7Si1.1Cx was proposed for magnetic systems using Ericsson cycle for refrigeration close to room temperature. The obtained entropy change of the composite remains approximately constant in this temperature range.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Neutron diffraction study of hexagonal manganite YMnO3, HoMnO3, and ErMnO3 epitaxial films

I. Gélard, C. Dubourdieu, S. Pailhès, S. Petit, and Ch. Simon

Appl. Phys. Lett. 92, 232506 (2008); http://dx.doi.org/10.1063/1.2943276 (3 pages) | Cited 12 times

Online Publication Date: 13 June 2008

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The antiferromagnetic phase transition in epitaxial RMnO3 (R = Y,Ho,Er) films of thickness 450–500 nm was investigated by neutron diffraction by recording the intensity variation of magnetic reflections as a function of temperature. For YMnO3 and ErMnO3, the Néel temperature for the Mn3+ ions ordering is of 66 and 68 K, respectively. For HoMnO3, the magnetic 011 reflection, which normally appears in bulk, is very weak and thus the onset of the Mn3+ ordering is not clearly observed; at 50 K there is a magnetic phase transition, which temperature corresponds to the reorientation temperature in bulk HoMnO3.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Ee Antiferromagnetics
68.55.jd Thickness

Room-temperature ferromagnetism in the Co-doped Ba0.5Sr0.5TiO3 thin films

L. B. Luo, Y. G. Zhao, H. F. Tian, J. J. Yang, H. Y. Zhang, J. Q. Li, J. J. Ding, B. He, S. Q. Wei, and C. Gao

Appl. Phys. Lett. 92, 232507 (2008); http://dx.doi.org/10.1063/1.2945282 (3 pages) | Cited 13 times

Online Publication Date: 13 June 2008

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The authors report the room-temperature ferromagnetism in the epitaxial thin films of 3% Co-doped Ba0.5Sr0.5TiO3 (CBSTO) grown by pulsed laser deposition. These films show the single phase character with Co dopants in the +2 state. More interestingly, ferromagnetic and ferroelectric transitions were observed at 570 and 150 K, respectively. The CBSTO films also show the exchange bias effect manifested by the negative shift and training effect of the hysteresis loops at 5 K. This work demonstrates that ferromagnetism can be induced in the ferroelectric materials, which is significant for shedding light on the mechanism of dopant induced ferromagnetism in insulators and applications.
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75.70.Ak Magnetic properties of monolayers and thin films
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.80.+q Magnetomechanical effects, magnetostriction
77.55.-g Dielectric thin films
77.80.B- Phase transitions and Curie point
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
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