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10 Dec 2007

Volume 91, Issue 24, Articles (24xxxx)

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Appl. Phys. Lett. 91, 241101 (2007); http://dx.doi.org/10.1063/1.2821382 (3 pages)

S. N. Goda, S. Sensarn, M. Y. Shverdin, and G. Y. Yin
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Spin-torque-driven vortex dynamics in a spin-valve pillar with a perpendicular polarizer

Yaowen Liu, Huan He, and Zongzhi Zhang

Appl. Phys. Lett. 91, 242501 (2007); http://dx.doi.org/10.1063/1.2822436 (3 pages) | Cited 25 times

Online Publication Date: 10 December 2007

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Spin-torque-driven vortex dynamics are studied by micromagnetic modeling in a spin-valve pillar which contains a perpendicular polarizer and a vortex free layer. Two kinds of transient oscillations mediated by the vortex-core motion are observed. The oscillations are treated as the competition among the spin torque, gyroforce, Gilbert damping, and the restoring force, governed by the generalized Thiele equation [ A. A. Thiele, J. Appl. Phys. 45, 377 (1974) ]. The fundamental frequency is dominated by the gyrotropic motion, while the high-frequency oscillation is triggered by the balance of the spin torque and demagnetizing field. The polarity of the vortex core can be switched through a vortex-antivortex pair creation and annihilation process.
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72.25.-b Spin polarized transport
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields

Correlation between photoluminescence and magnetic properties of GaMnN films

N. Nepal, Amr M. Mahros, S. M. Bedair, N. A. El-Masry, and J. M. Zavada

Appl. Phys. Lett. 91, 242502 (2007); http://dx.doi.org/10.1063/1.2823602 (3 pages) | Cited 2 times

Online Publication Date: 10 December 2007

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GaMnN films grown by metal-organic chemical vapor deposition were studied by photoluminescence (PL) spectroscopy and hysteresis measurements. Depending on the growth conditions of these GaMnN films, hysteresis measurements along the easy axis of magnetization show a transformation from magnetic to nonmagnetic behavior. The PL spectra of both magnetic and nonmagnetic GaMnN films exhibited GaN band edge and deep-level impurity transitions at 3.4 and 1.3 eV, respectively. The PL emission intensity of the 1.3 eV emission peak is stronger considerably for magnetic GaMnN films and is believed to be due to the Mn3+ intraband transition.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
75.50.Pp Magnetic semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.05.Ea III-V semiconductors

Room temperature magnetocaloric effect in Ni–Mn–In

P. A. Bhobe, K. R. Priolkar, and A. K. Nigam

Appl. Phys. Lett. 91, 242503 (2007); http://dx.doi.org/10.1063/1.2823601 (3 pages) | Cited 34 times

Online Publication Date: 11 December 2007

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We have studied the effect of magnetic field on a nonstoichiometric Heusler alloy Ni50Mn35In15 that undergoes a martensitic as well as a magnetic transition near room temperature. Temperature dependent magnetization measurements demonstrate the influence of magnetic field on the structural phase transition temperature. From the study of magnetization as a function of applied field, we show the occurrence of inverse-magnetocaloric effect associated with this magneto-structural transition. The magnetic entropy change attains a value as high as 25 J/kg K (at 5 T field) at room temperature as the alloy transforms from the austenitic to martensitic phase with a concomitant magnetic ordering.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.05.Bx Metals, semimetals, and alloys

Effects of Ta seed layer and annealing on magnetoresistance in CoFe/Pd-based pseudo-spin-valves with perpendicular anisotropy

Randall Law, Rachid Sbiaa, Thomas Liew, and Tow Chong Chong

Appl. Phys. Lett. 91, 242504 (2007); http://dx.doi.org/10.1063/1.2824832 (3 pages) | Cited 32 times

Online Publication Date: 12 December 2007

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We have studied the switching characteristics and magnetoresistance of pseudo-spin-valves with perpendicular anisotropy based on CoFe/Pd multilayers. In unpatterned thin films without exchange biasing, a maximum current-in-plane giant magnetoresistance of 7% was achieved, the highest reported to date in perpendicular pseudo-spin-valves. A Ta seed layer and the fcc (111) orientation of Pd was shown to be important in order to achieve good perpendicular anisotropy and sharp switching behavior. The improvement in perpendicular anisotropy and decay in magnetoresistance upon postdeposition annealing have been attributed to the formation of CoPd alloys at the CoFe/Pd interfaces.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Gw Magnetic anisotropy
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Nt Magnetic annealing and temperature-hysteresis effects
75.47.De Giant magnetoresistance

Particular strain relaxation for La0.8Ba0.2MnO3 films on SrTiO3 (100) substrates

Hsiung Chou, C. B. Wu, F. P. Yun, Z. H. Zhang, and W. K. Chu

Appl. Phys. Lett. 91, 242505 (2007); http://dx.doi.org/10.1063/1.2824482 (3 pages) | Cited 2 times

Online Publication Date: 14 December 2007

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A particular two stage strain relaxation phenomenon on La0.8Ba0.2MnO3 thick films has been observed. A fully strained bottom layer near the film/substrate interface consists of a moderate density of dislocations, while a top layer exhibits a high density of dislocations, becoming denser as it nears the surface of the film. This phenomenon can be attributed to the partial diffusion of the substrate element, Sr, into the bottom layer of the film, which reduces its lattice constant, and to the sudden change of the lattice constants at the bottom-top-layer interface due to the stoppage of Sr diffusion.
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68.35.Fx Diffusion; interface formation
61.72.Lk Linear defects: dislocations, disclinations
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