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4 Sep 2006

Volume 89, Issue 10, Articles (10xxxx)

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Appl. Phys. Lett. 89, 103101 (2006); http://dx.doi.org/10.1063/1.2345352 (3 pages)

F. Hao and P. Nordlander
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Nuclear magnetic resonance study of the Ru/Mn valence states and magnetic interactions in SrRu0.9Mn0.1O3

Z. H. Han, J. I. Budnick, W. A. Hines, B. Dabrowski, and T. Maxwell

Appl. Phys. Lett. 89, 102501 (2006); http://dx.doi.org/10.1063/1.2345595 (3 pages) | Cited 9 times

Online Publication Date: 5 September 2006

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The substitution of Mn for Ru in SrRuO3 suppresses the ferromagnetic (FM) order monotonically at low concentration (<0.39) and induces antiferromagnetic (AFM) order at high concentration (>0.39). In an attempt to understand how the Mn substitution initially modifies the magnetic interactions in SrRu1−xMnxO3, a polycrystalline SrRu0.9Mn0.1O3 sample was prepared and studied by math and math spin-echo nuclear magnetic resonance (NMR). math NMR reveals that the Mn dopants are in an intermediate Mn3+/4+ valence state due to fast electron hopping. The magnetic interaction between the Mn ions is FM, mediated by the double exchange mechanism. The Ru4+ hyperfine field is reduced due to an AFM coupling with the Mn moments, which shifts the Ru NMR peaks to lower frequencies. The suppression of the FM ordering temperature in SrRu1−xMnxO3 is attributed to the interruption of the itinerancy of the Ru 4d electrons by Mn substitution.
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75.30.Et Exchange and superexchange interactions
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Ee Antiferromagnetics
71.70.Jp Nuclear states and interactions
76.60.Lz Spin echoes

Current-induced magnetization switching under magnetic field applied along the hard axis in MgO-based magnetic tunnel junctions

T. Inokuchi, H. Sugiyama, Y. Saito, and K. Inomata

Appl. Phys. Lett. 89, 102502 (2006); http://dx.doi.org/10.1063/1.2338016 (3 pages) | Cited 10 times

Online Publication Date: 5 September 2006

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The authors have investigated the dependence of the critical current density (Jc) for the current-induced magnetization switching (CIMS) on external magnetic fields applied along the hard axis of a free layer (Hhard) and on the duration of pulse current in MgO-based magnetic tunnel junctions. The Jc and the intrinsic current density (Jc0), derived from the dependence of the Jc on the pulse duration, decreased as ∣Hhard∣ increased. These reductions of Jc and Jc0 would be attributed to the decrease of energy barrier for CIMS and the increase of the spin transfer efficiency.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
74.25.Sv Critical currents

Evidence of metallic clustering in annealed Ga1−xMnxAs from atypical scaling behavior of the anomalous Hall coefficient

H. K. Choi, Y. S. Kim, S. S. A. Seo, I. T. Jeong, W. O. Lee, Y. S. Oh, K. H. Kim, J. C. Woo, T. W. Noh, Z. G. Khim, Y. D. Park, and S. H. Chun

Appl. Phys. Lett. 89, 102503 (2006); http://dx.doi.org/10.1063/1.2344932 (3 pages) | Cited 7 times

Online Publication Date: 5 September 2006

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The anomalous Hall coefficient (Rs) and longitudinal resistivity (ρxx) scaling relationship (RS = cρxxn) for a series of annealed Ga1−xMnxAs epilayers (x ≈ 0.055) are investigated. As-grown samples exhibit a scaling parameter n ∼ 1 and samples annealing near the optimal annealing temperature, n ∼ 2. For annealing temperatures far above the optimum they observe scaling with n>3, which is similar to the behavior of certain inhomogeneous systems. Optical spectroscopy measurements also reveal an enhancement of the absorption coefficient in these samples for photons of energy around 1 eV. These atypical behaviors are characteristic of spherical resonance from metallic inclusions.
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75.50.Pp Magnetic semiconductors
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.72.Cc Kinetics of defect formation and annealing
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects

Magnetic domain wall serial-in parallel-out shift register

D. A. Allwood, Gang Xiong, and R. P. Cowburn

Appl. Phys. Lett. 89, 102504 (2006); http://dx.doi.org/10.1063/1.2345032 (3 pages) | Cited 8 times

Online Publication Date: 6 September 2006

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We demonstrate a three-terminal magnetic nanowire logic junction that combines logical NOT and signal fan-out operations. The behavior and performance of the three-terminal device are similar to those of previous two-terminal NOT gates. However, the third terminal provides an additional, noninverted output. We have demonstrated the versatility that this brings by integrating a chain of the three-terminal hybrid elements with other nanowire logic elements to create a serial-in parallel-out shift register.
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84.30.Sk Pulse and digital circuits
85.70.-w Magnetic devices

Evidence of room temperature sp-d exchange in InMnAs epitaxial films

P. T. Chiu and B. W. Wessels

Appl. Phys. Lett. 89, 102505 (2006); http://dx.doi.org/10.1063/1.2345604 (3 pages) | Cited 5 times

Online Publication Date: 7 September 2006

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Reflection magnetic circular dichroism (MCD) spectrum was measured from 1.6 to 3.0 eV to determine the nature of sp-d exchange in epitaxial InMnAs thin films. At room temperature and an applied field of 0.5 T, the MCD spectrum is composed of two types of transitions: a negative peak centered between 2.60 and 2.68 eV and a broad, negative response from 1.6 to 3.0 eV. For both transitions, ferromagnetic hysteresis and saturation are observed. The negative peak is attributed to the L-point critical transitions of InMnAs at 2.53 and 2.79 eV, respectively. The MCD enhancement at the L point is consistent with room temperature sp-d exchange splitting in metal organic vapor phase epitaxy grown InMnAs. The sp-d exchange is attributed to magnetic Mn dimers and trimers in the InMnAs. In contrast, the broad, featureless spectral response is consistent with spin dependent transitions between the Mn impurity band and conduction band.
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75.50.Pp Magnetic semiconductors
71.55.Eq III-V semiconductors
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
71.70.Gm Exchange interactions
75.30.Et Exchange and superexchange interactions

Preparation and photoabsorption characterization of BiFeO3 nanowires

F. Gao, Y. Yuan, K. F. Wang, X. Y. Chen, F. Chen, J.-M. Liu, and Z. F. Ren

Appl. Phys. Lett. 89, 102506 (2006); http://dx.doi.org/10.1063/1.2345825 (3 pages) | Cited 86 times

Online Publication Date: 7 September 2006

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Perovskite-type polycrystalline BiFeO3 (BFO) nanowires ( ∼ 50 nm in diameter and ∼ 5 μm in length) were synthesized using the anodized alumina template technique. An energy band gap of ∼ 2.5 eV was determined from the UV-visible diffuse reflectance spectrum, and its photocatalytic ability to produce O2 was revealed under UV irradiation. Weak ferromagnetism at room temperature and superparamagnetism at low temperature were observed for the BFO nanowires, different from the antiferromagnetic order in bulk BFO, reflecting the significant size effects on the magnetic ordering of BFO.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Tt Fine-particle systems; nanocrystalline materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.40.Ha Other nonmetallic inorganics
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