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15 May 2006

Volume 88, Issue 20, Articles (20xxxx)

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Appl. Phys. Lett. 88, 203101 (2006); http://dx.doi.org/10.1063/1.2203932 (3 pages)

Andrea Ponzoni, Elisabetta Comini, Giorgio Sberveglieri, Jun Zhou, Shao Zhi Deng, Ning Sheng Xu, Yong Ding, and Zhong Lin Wang
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Spin-polarized transport in hybrid (Zn,Cr)Te/Al2O3/Co magnetic tunnel junctions

W. G. Wang, C. Ni, T. Moriyama, J. Wan, E. Nowak, and John Q. Xiao

Appl. Phys. Lett. 88, 202501 (2006); http://dx.doi.org/10.1063/1.2205177 (3 pages) | Cited 16 times

Online Publication Date: 17 May 2006

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Tunnel magnetoresistance (TMR) of 21% is observed at low temperature in hybrid magnetic tunnel junctions (MTJs) composed of a magnetic semiconductor (Zn,Cr)Te and Co electrodes separated by an alumina barrier. The TMR is observed up to 250 K, which is a considerable improvement over previous work on MTJs with semiconductor electrodes. The temperature and bias dependence of the TMR are consistent with a transport model involving spin-polarized tunneling and spin-independent hopping through impurity states.
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75.47.-m Magnetotransport phenomena; materials for magnetotransport
72.25.-b Spin polarized transport
75.50.Cc Other ferromagnetic metals and alloys
75.50.Pp Magnetic semiconductors
71.55.-i Impurity and defect levels

Spin transfer by nonuniform current injection into a nanomagnet

O. Ozatay, N. C. Emley, P. M. Braganca, A. G. F. Garcia, G. D. Fuchs, I. N. Krivorotov, R. A. Buhrman, and D. C. Ralph

Appl. Phys. Lett. 88, 202502 (2006); http://dx.doi.org/10.1063/1.2206683 (3 pages) | Cited 21 times

Online Publication Date: 18 May 2006

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We have used nanofabrication techniques to incorporate an ∼ 20–30 nm diameter nanoaperture within a 150×250 nm2 elliptical magnetic multilayer to enable the localized injection of spin-polarized currents into a thin film nanomagnet. This results in very low spin transfer currents being required for at least partial nanomagnet reversal as well as for onset of dynamic precession. Micromagnetic simulations using Landau-Liftshitz-Gilbert equation with a spin-torque term indicate that reversal occurs via domain nucleation at the injection site followed by domain wall propagation away from the aperture, with the nanomagnet ending in one of several different states depending upon the current amplitude.
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72.25.Ba Spin polarized transport in metals
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Tt Fine-particle systems; nanocrystalline materials

Effect of strain on structure and charge order transitions in epitaxial Bi0.4Ca0.6MnO3 films on perovskite (001) and (011) substrates

Dae Ho Kim, Hans M. Christen, Maria Varela, Ho Nyung Lee, and Douglas H. Lowndes

Appl. Phys. Lett. 88, 202503 (2006); http://dx.doi.org/10.1063/1.2205753 (3 pages) | Cited 17 times

Online Publication Date: 18 May 2006

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The effect of epitaxial strain on the charge order (CO) transition in Bi0.4Ca0.6MnO3 films was studied by varying the strain’s strength and symmetry via the use of SrTiO3 and LaAlO3 substrates having different crystallographic orientations. The film on pseudocubic (001) LaAlO3, under symmetric compressive strain, exhibits a clear CO transition. In the film on a (001) SrTiO3 substrate, under symmetric tensile strain, highly segregated line-shaped features in the Bi distribution are seen in Z-contrast scanning transmission microscopy, accompanied by a strongly broadened CO transition. The asymmetric tensile stress on (011) SrTiO3 results in an apparent compressive strain state with a deviation from tetragonality (i.e., γ ≠ 90°), accompanied by the sharpest CO transition. These comparisons illustrate the importance of considering both the strength and symmetry of epitaxial strain.
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68.60.Bs Mechanical and acoustical properties
71.45.-d Collective effects
75.50.Dd Nonmetallic ferromagnetic materials
68.55.-a Thin film structure and morphology

Powder magnetoresistance of Co2Cr0.6Fe0.4Al/Al2O3 powder compacts

T. Block, S. Wurmehl, C. Felser, and J. Windeln

Appl. Phys. Lett. 88, 202504 (2006); http://dx.doi.org/10.1063/1.2200571 (3 pages) | Cited 7 times

Online Publication Date: 19 May 2006

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We report on the magnetotransport properties of Co2Cr0.6Fe0.4Al mixed with insulating Al2O3. The powder compacts show a maximum magnetoresistance of 88% at a saturation moment of 0.125 T at 295 K. Different explanations for the reversible mechanism will be discussed, such as tunneling between contiguous ferromagnetic grains, particle movement, and magnetostriction. The effect in Co2Cr0.6Fe0.4Al/Al2O3 powder compacts is the largest room temperature magnetoresistance that has been measured until now.
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72.20.My Galvanomagnetic and other magnetotransport effects
61.43.Gt Powders, porous materials
75.50.Bb Fe and its alloys
75.30.Cr Saturation moments and magnetic susceptibilities
75.80.+q Magnetomechanical effects, magnetostriction
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