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12 Sep 2011

Volume 99, Issue 11, Articles (11xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 99, 113501 (2011); http://dx.doi.org/10.1063/1.3634072 (3 pages)

Asif Islam Khan, Debanjan Bhowmik, Pu Yu, Sung Joo Kim, Xiaoqing Pan, Ramamoorthy Ramesh, and Sayeef Salahuddin
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Fluxgate based detection of magnetic nanoparticle dynamics in a rotating magnetic field

Jan Dieckhoff, Meinhard Schilling, and Frank Ludwig

Appl. Phys. Lett. 99, 112501 (2011); http://dx.doi.org/10.1063/1.3639276 (3 pages) | Cited 3 times

Online Publication Date: 14 September 2011

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We have developed a measurement setup allowing the investigation of the dynamics of magnetic nanoparticle suspensions in a rotating magnetic field. To determine the vector of the sample magnetization, sensitive fluxgate magnetometers are utilized detecting the sample’s stray field. The phase lag between sample magnetization and rotating magnetic field vector is determined via the cross correlation spectrum. The phase lag spectra measured for various rotating field amplitudes on aqueous magnetite nanoparticle suspensions show good agreement with theory if the multidispersity of core and hydrodynamic size is taken into account.
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07.55.Ge Magnetometers for magnetic field measurements
07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Tt Fine-particle systems; nanocrystalline materials

Electronic depiction of magnetic origin in undoped and Fe doped TiO2−d epitaxial thin films

Komal Bapna, R. J. Choudhary, S. K. Pandey, D. M. Phase, S. K. Sharma, and M. Knobel

Appl. Phys. Lett. 99, 112502 (2011); http://dx.doi.org/10.1063/1.3640212 (3 pages) | Cited 6 times

Online Publication Date: 15 September 2011

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We have investigated the electronic and magnetic properties of the pulsed laser deposited epitaxial thin films of undoped and Fe doped (4 at. %) anatase TiO2−d by photoemission, magnetization measurements, and ab-initio band structure calculations. These films show room temperature magnetic ordering. It is observed that Fe ions hybridize with the oxygen vacancy induced Ti3+ defect states. Our study reveals the formation of local magnetic moment at Ti and Fe sites to be responsible for magnetic ordering. A finite density of states at the Fermi level in both undoped and Fe doped films is also observed, suggesting their degenerate semiconducting nature.
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71.20.Nr Semiconductor compounds
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.15.Fg Pulsed laser ablation deposition
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Cr Saturation moments and magnetic susceptibilities
73.20.At Surface states, band structure, electron density of states

Magnetic field influence on the transient photoresistivity of defect-induced magnetic ZnO films

C. Zapata, M. Khalid, G. Simonelli, M. Villafuerte, S. P. Heluani, and P. Esquinazi

Appl. Phys. Lett. 99, 112503 (2011); http://dx.doi.org/10.1063/1.3640231 (3 pages) | Cited 2 times

Online Publication Date: 16 September 2011

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Magnetic field dependent photoresistivity was measured at 280 K in ZnO ferromagnetic films grown on r-plane Al2O3 under a N2 atmosphere. A correlation between the negative magneto photoresistivity and the existence of defect-induced magnetic order was found. The effect of magnetic field on the transient photoresistivity is to slow down the recombination process enhancing the photocarriers density. The experimental results demonstrate the possibility of tuning photocarriers life time using magnetic field in diluted magnetic semiconductors.
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73.50.Pz Photoconduction and photovoltaic effects
81.05.Dz II-VI semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials

Switching-probability distribution of spin-torque switching in MgO-based magnetic tunnel junctions

Takayuki Seki, Akio Fukushima, Hitoshi Kubota, Kay Yakushiji, Shinji Yuasa, and Koji Ando

Appl. Phys. Lett. 99, 112504 (2011); http://dx.doi.org/10.1063/1.3637545 (3 pages) | Cited 2 times

Online Publication Date: 16 September 2011

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The time-evolution of the switching characteristics of spin-torque switching in MgO-based magnetic tunnel junctions (MTJs) during more than 109 write/read cycles was measured experimentally. In the measurements, the magnetic field and current conditions were chosen to give a switching probability (Psw) of about 0.5, where Psw is most sensitive to changes in the magnetic properties of an MTJ cell. Interestingly, some MTJ cells showed small jumps of Psw, which can be attributed to random transitions between states with slightly different magnetic configurations. Such time-evolution measurement can be used to evaluate the stability of the switching characteristics of memory cells.
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85.75.Dd Magnetic memory using magnetic tunnel junctions
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
02.70.Rr General statistical methods
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