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7 Aug 2006

Volume 89, Issue 6, Articles (06xxxx)

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Appl. Phys. Lett. 89, 062501 (2006); http://dx.doi.org/10.1063/1.2259813 (3 pages)

Sangkook Choi, Ki-Suk Lee, and Sang-Koog Kim
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Spin-wave interference

Sangkook Choi, Ki-Suk Lee, and Sang-Koog Kim

Appl. Phys. Lett. 89, 062501 (2006); http://dx.doi.org/10.1063/1.2259813 (3 pages) | Cited 20 times

Online Publication Date: 7 August 2006

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Spin-wave interference is demonstrated in the micromagnetic modeling of a specially designed geometry made of variously shaped magnetic thin-film waveguides. When spin waves are diffracted through two separate openings, corresponding to the two pinholes in the second screen of Young’s apparatus, they interfere constructively or destructively in a magnetic medium, thereby showing distinct interference patterns. Furthermore, the radiation, propagation, transmission, and dispersion behaviors of spin waves as well as the filtering of their lower frequencies are investigated in the present modeling study. These results directly confirm not only the wave characteristics of spin waves traveling at ultrafast speeds in variously shaped magnetic waveguides but also their interference effect, that is similar to that observed in well-known Young’s double slit experiment with light.
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75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.70.Ak Magnetic properties of monolayers and thin films
84.40.Az Waveguides, transmission lines, striplines

Evidence for spin injection in a single metallic nanoparticle: A step towards nanospintronics

A. Bernand-Mantel, P. Seneor, N. Lidgi, M. Muñoz, V. Cros, S. Fusil, K. Bouzehouane, C. Deranlot, A. Vaures, F. Petroff, and A. Fert

Appl. Phys. Lett. 89, 062502 (2006); http://dx.doi.org/10.1063/1.2236293 (3 pages) | Cited 41 times

Online Publication Date: 7 August 2006

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We have fabricated nanometer-sized magnetic tunnel junctions using a conductive tip nanoindentation technique in order to study the transport properties of a single metallic nanoparticle. Coulomb blockade effects show clear evidence for single-electron tunneling through a single 2.5 nm Au cluster. The observed magnetoresistance is the signature of spin conservation during the transport process through a nonmagnetic cluster.
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75.50.Tt Fine-particle systems; nanocrystalline materials
73.63.Bd Nanocrystalline materials
72.25.Ba Spin polarized transport in metals
73.23.Hk Coulomb blockade; single-electron tunneling
75.47.Np Metals and alloys

Ferromagnetism and colossal magnetic moment in Gd-focused ion-beam-implanted GaN

S. Dhar, T. Kammermeier, A. Ney, L. Pérez, K. H. Ploog, A. Melnikov, and A. D. Wieck

Appl. Phys. Lett. 89, 062503 (2006); http://dx.doi.org/10.1063/1.2267900 (3 pages) | Cited 47 times

Online Publication Date: 7 August 2006

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The structural and the magnetic properties of Gd-focused ion-beam-implanted GaN layers are studied. Gd3+ ions were uniformly implanted in molecular beam epitaxy grown GaN layers at room temperature with an energy of 300 keV at doses ranging from 2.4×1011 to 1.0×1015 cm−2 which corresponds to an average Gd concentration range of 2.4×1016–1.0×1020 cm−3. The implanted samples were not subjected to any annealing treatment. No secondary phase related to Gd was detected by x-ray diffraction in these layers. Magnetic characterization with superconducting quantum interference device reveals a colossal magnetic moment of Gd and ferromagnetism with an order temperature above room temperature similar to that found in epitaxially grown Gd-doped GaN layers. The effective magnetic moment per Gd atom in these samples is, however, found to be an order of magnitude larger than that found in epitaxially grown layers for a given Gd concentration which indicates that the defects play an important role in giving rise to this effect.
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81.05.Ea III-V semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Cr Saturation moments and magnetic susceptibilities
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Pp Magnetic semiconductors
61.72.uj III-V and II-VI semiconductors

Strong magnetocaloric effects in La1−zCez(Fex−yMnySi1−x)13 at low temperatures

S. Fujieda, A. Fujita, N. Kawamoto, and K. Fukamichi

Appl. Phys. Lett. 89, 062504 (2006); http://dx.doi.org/10.1063/1.2227631 (3 pages) | Cited 7 times

Online Publication Date: 7 August 2006

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The Curie temperature TC of La1−zCez(Fex−yMnySi1−x)13 is decreased by adjusting the composition, and hence the itinerant-electron metamagnetic transition is observed at 5 K in La0.75Ce0.25(Fe0.850Mn0.035Si0.110)13 after zero-field cooling. As a result, the La1−zCez(FexMnySi1−x)13 compounds exhibit strong magnetocaloric effects in relatively low magnetic fields in a wide range of temperatures between about 19 and 180 K. Consequently, the La1−zCez(Fex−yMnySi1−x)13 compounds are useful for the magnetic refrigerants working at low temperatures.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Bb Fe and its alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Cu-doped GaN: A dilute magnetic semiconductor from first-principles study

R. Q. Wu, G. W. Peng, L. Liu, Y. P. Feng, Z. G. Huang, and Q. Y. Wu

Appl. Phys. Lett. 89, 062505 (2006); http://dx.doi.org/10.1063/1.2335773 (3 pages) | Cited 47 times

Online Publication Date: 8 August 2006

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First-principles calculations based on spin density functional theory are performed to study the spin-resolved electronic properties of GaN doped with 6.25% of Cu. The Cu dopants are found spin polarized and the calculated band structures suggest a 100% polarization of the conduction carriers. The Cu-doped GaN favors ferromagnetic ground state which can be explained in terms of p‐d hybridization mechanism, and a Curie temperature around 350 K can be expected. These results suggest that the Cu-doped GaN is a promising dilute magnetic semiconductor free of magnetic precipitates and may find applications in the field of spintronics.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Nr Semiconductor compounds
72.25.Dc Spin polarized transport in semiconductors
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
61.72.uj III-V and II-VI semiconductors

Indication of intrinsic room-temperature ferromagnetism in Ti1−xCoxO2−δ thin film: An x-ray magnetic circular dichroism study

K. Mamiya, T. Koide, A. Fujimori, H. Tokano, H. Manaka, A. Tanaka, H. Toyosaki, T. Fukumura, and M. Kawasaki

Appl. Phys. Lett. 89, 062506 (2006); http://dx.doi.org/10.1063/1.2236829 (3 pages) | Cited 25 times

Online Publication Date: 9 August 2006

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Soft x-ray magnetic circular dichroism (XMCD) measurements at the Co L2,3 edges of Co-doped rutile TiO2 at room temperature revealed clear multiplet features characteristic of ferromagnetic Co2+ ions coordinated by O2− ions, being in sharp contrast to the featureless XMCD spectrum of Co metal or metallic clusters. The absorption and XMCD spectra agree well with a full atomic-multiplet calculation for the Co2+ high-spin state in the D2h-symmetry crystal field at the Ti site in rutile TiO2. The results indicate that the ferromagnetism arises from the Co2+ ions substituting the Ti4+ ions.
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75.50.Pp Magnetic semiconductors
78.20.Ls Magneto-optical effects
61.72.up Other materials
75.50.Dd Nonmetallic ferromagnetic materials

Quadratic mixing of radio frequency signals using superconducting quantum interference filters

P. Caputo, J. Tomes, J. Oppenländer, Ch. Häussler, A. Friesch, T. Träuble, and N. Schopohl

Appl. Phys. Lett. 89, 062507 (2006); http://dx.doi.org/10.1063/1.2335368 (3 pages) | Cited 5 times

Online Publication Date: 9 August 2006

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The authors demonstrate quadratic mixing of weak time harmonic electromagnetic fields applied to superconducting quantum interference filters (SQIFs), manufactured from high-Tc grain boundary Josephson junctions and operated in active microcooler. The authors use the parabolic shape of the dip in the dc voltage output around B = 0 to mix quadratically two external rf signals, at frequencies f1 and f2 well below the Josephson frequency fJ, and detect the corresponding mixing signal at ∣f1−f2∣. Quadratic mixing also takes place when the SQIF is operated without magnetic shield. The experimental results are well described by a simple analytical model based on the adiabatic approximation.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.30.Vn Filters

Modified Sagnac interferometer for high-sensitivity magneto-optic measurements at cryogenic temperatures

Jing Xia, Peter T. Beyersdorf, M. M. Fejer, and Aharon Kapitulnik

Appl. Phys. Lett. 89, 062508 (2006); http://dx.doi.org/10.1063/1.2336620 (3 pages) | Cited 7 times

Online Publication Date: 9 August 2006

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The authors describe a geometry for a Sagnac interferometer with a zero-area Sagnac loop for measuring the magneto-optic Kerr effect at cryogenic temperatures. The apparatus is capable of measuring absolute Kerr rotation without any modulation of the magnetic state of the sample and is intrinsically immune to reciprocal effects such as linear birefringence and thermal fluctuations. A single strand of polarization-maintaining fiber is fed into a He-3 cryostat, eliminating the need for optical viewports. With an optical power of only 10 μW, they demonstrate static Kerr measurements with a shot-noise-limited sensitivity of 1×10−7 rad/math down to 0.5 K.
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07.60.Ly Interferometers
78.20.Ls Magneto-optical effects
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
05.40.Ca Noise

Evidence of unquenched Re orbital magnetic moment in AA′FeReO6 double perovskites

M. Sikora, Cz. Kapusta, M. Borowiec, C. J Oates, V. Prochazka, D. Rybicki, D. Zajac, J. M De Teresa, C. Marquina, and M. R Ibarra

Appl. Phys. Lett. 89, 062509 (2006); http://dx.doi.org/10.1063/1.2234292 (3 pages) | Cited 16 times

Online Publication Date: 10 August 2006

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Spin and orbital magnetic moments of rhenium in AA′FeReO6 double perovskites (A,A′ = Ba, Sr, and Ca) have been directly probed employing x-ray magnetic circular dichroism at the Re L2,3 edges. A considerable orbital magnetic moment is observed in all the compounds studied, which confirm theoretical predictions of unquenched Re orbital moment despite its octahedral coordination. Relative orbital-to-spin moment ratio alters with lattice distortion from mL/mS = −0.285 to −0.337 from Ba2FeReO6 to Ca2FeReO6, respectively. Moreover, the spin moment of Re ion scales with Curie temperature, the most relevant property in spin electronics application of the compounds studied.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Dd Nonmetallic ferromagnetic materials
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)

Magnetic circular dichroism of ferromagnetic Co2+-doped ZnO

Kevin R. Kittilstved, Jialong Zhao, William K. Liu, J. Daniel Bryan, Dana A. Schwartz, and Daniel R. Gamelin

Appl. Phys. Lett. 89, 062510 (2006); http://dx.doi.org/10.1063/1.2221871 (3 pages) | Cited 16 times

Online Publication Date: 11 August 2006

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Cobalt-doped ZnO (Co2+:ZnO) films were studied by magnetic circular dichroism (MCD) spectroscopy. A broad 300 K ferromagnetic MCD signal was observed between 1.4 and 4.0 eV after exposure of paramagnetic Co2+:ZnO films to zinc metal vapor, attributed to low-energy photoionization transitions originating from a spin-split donor impurity band in ferromagnetic n-type Co2+:ZnO.
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78.20.Ls Magneto-optical effects
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
75.20.Ck Nonmetals
71.55.Gs II-VI semiconductors

Oxygen-redistribution-induced disorder and magnetotransport properties of Sm0.55Sr0.45MnO3 manganites

M. Egilmez, K. H. Chow, and J. Jung

Appl. Phys. Lett. 89, 062511 (2006); http://dx.doi.org/10.1063/1.2335574 (3 pages) | Cited 11 times

Online Publication Date: 11 August 2006

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The authors studied the effects of oxygen-redistribution-induced disorder on the magnetotransport of Sm0.55Sr0.45MnO3 manganites near the metal-insulator transition. Oxygen redistribution in the sample was obtained by annealing at 325 °C in vacuum. The temperature dependences of resistivity and magnetoresistance were measured as a function of the annealing time. The authors observed a dramatic increase in the magnitude of the resistivity peak at the metal-insulator transition and a reduction of its width after an initial short-time annealing, followed by a logarithmic increase of the resistivity with annealing time. The data agree qualitatively with phase-separation theories for colossal magnetoresistance manganites.
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75.47.Gk Colossal magnetoresistance
75.47.Lx Magnetic oxides
71.30.+h Metal-insulator transitions and other electronic transitions
81.40.Gh Other heat and thermomechanical treatments

Domain wall assisted magnetic recording

A. Yu. Dobin and H. J. Richter

Appl. Phys. Lett. 89, 062512 (2006); http://dx.doi.org/10.1063/1.2335590 (3 pages) | Cited 73 times

Online Publication Date: 11 August 2006

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Using numerical and analytical micromagnetics the authors calculated the switching fields and energy barriers of the composite (exchange spring) magnetic recording media, which consist of layers with high and low magnetocrystalline anisotropies. The authors demonstrate that the ultimate potential of the composite media is realized if the interfacial domain wall fits inside the layers. The switching occurs via domain wall nucleation, compression in the applied field, depinning, and propagation through the hard/soft interface. The authors demonstrate that the domain wall assisted magnetic recording offers up to a threefold areal density gain over conventional single layer recording.
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75.50.Ss Magnetic recording materials
75.60.Ch Domain walls and domain structure
75.30.Gw Magnetic anisotropy
75.40.Mg Numerical simulation studies
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