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25 Oct 2004

Volume 85, Issue 17, pp. 3657-3939

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Appl. Phys. Lett. 85, 3851 (2004); http://dx.doi.org/10.1063/1.1808886 (3 pages)

P. Guha, S. Kar, and S. Chaudhuri
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Suppression of spin accumulation in nonmagnet due to ferromagnetic ohmic contact

T. Kimura, J. Hamrle, Y. Otani, K. Tsukagoshi, and Y. Aoyagi

Appl. Phys. Lett. 85, 3795 (2004); http://dx.doi.org/10.1063/1.1811801 (2 pages) | Cited 17 times

Online Publication Date: 29 October 2004

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We experimentally demonstrate that the ohmic contact of a Ni–Fe wire additionally connected to a Cu strip between an injector and detector in a nonlocal spin-valve structure signicantly suppresses the spin polarization induced in the Cu strip. This behavior is attributable to spin current absorption into the connected additional Ni–Fe wire.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Bb Fe and its alloys
72.25.Mk Spin transport through interfaces

Anistropic photoinduced magnetism of a RbjCok[Fe(CN)6]l⋅nH2O thin film

J.-H. Park, E. Čižmár, M. W. Meisel, Y. D. Huh, F. Frye, S. Lane, and D. R. Talham

Appl. Phys. Lett. 85, 3797 (2004); http://dx.doi.org/10.1063/1.1807963 (3 pages) | Cited 15 times

Online Publication Date: 29 October 2004

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A magneto-optically active thin film of RbjCok[Fe(CN)6]l⋅nH2O has been prepared using a sequential assembly method. Upon irradiation with light and at 5 K, the net magnetization of the film increased when the surface of the film was oriented parallel to the external magnetic field of 0.1 T. However, when the surface of the film was perpendicular to the field, the net magnetization decreased upon irradiation. The presence of dipolar fields and the low-dimensional nature of the system are used to describe the orientation dependence of the photoinduced magnetization. The ability to increase or decrease the photoinduced magnetization by changing the orientation of the system with respect to the field is a phenomenon that may be useful in future device applications.
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78.20.Ls Magneto-optical effects
75.50.Xx Molecular magnets
75.20.Ck Nonmetals
75.50.Gg Ferrimagnetics
75.70.Ak Magnetic properties of monolayers and thin films
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
75.30.Gw Magnetic anisotropy
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Precipitate-free films of La1−xSrxMnO3 grown on the substrates with artificial step edges

Y. Ishii, H. Sato, A. Sawa, T. Yamada, H. Akoh, K. Endo, M. Kawasaki, and Y. Tokura

Appl. Phys. Lett. 85, 3800 (2004); http://dx.doi.org/10.1063/1.1807969 (3 pages) | Cited 6 times

Online Publication Date: 29 October 2004

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We have fabricated precipitate-free La0.7Sr0.3MnO3 (LSMO) films by locating precipitate nucleation at artificial step edges patterned on SrTiO3 substrates and absorbing excess species of off-stoichiometry by getter effect. The precipitate-free and atomically flat area of about 10 μm width can be obtained along the step edges by pulsed-laser deposition at a substrate temperature Ts of ∼900 °C. Thermally activated processes are shown to be involved in such chemical reactions between the precipitates and surface migrating species. LSMO∕SrTiO3∕LSMO tunnel junctions fabricated by this method showed an excellent uniformity of the junction resistances.
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68.55.A- Nucleation and growth
61.72.Yx Interaction between different crystal defects; gettering effect
61.66.Bi Elemental solids
61.66.Dk Alloys
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.30.Mh Solid-phase precipitation
81.15.Fg Pulsed laser ablation deposition

Spin polarization and barrier-oxidation effects at the Co∕alumina interface in magnetic tunnel junctions

N. D. Telling, G. van der Laan, S. Ladak, and R. J. Hicken

Appl. Phys. Lett. 85, 3803 (2004); http://dx.doi.org/10.1063/1.1812383 (3 pages) | Cited 11 times

Online Publication Date: 29 October 2004

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The electronic structure and polarization in magnetic tunnel junctions prepared with varying degrees of barrier-layer oxidation have been studied using x-ray absorption spectroscopy across the Co L2,3 absorption edges. It was found that the Co electronic structure near the Co∕alumina interface tended to that of cobalt oxide as the barrier oxidation time was increased. However, the net Co 3d spin polarization, determined from x-ray magnetic circular dichroism, increased for moderate oxidation times compared to that obtained for an under-oxidized Co∕Al interface. It is proposed that the expected dilution of the measured polarization due to the formation of (room temperature) paramagnetic cobalt oxide, is offset by an increase in the Co 3d spin-polarization of the interface layer as the interface bonding changes from Co–Al to Co–O with increasing oxidation times.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.65.Mq Oxidation
75.20.En Metals and alloys
78.70.Dm X-ray absorption spectra
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
81.15.Cd Deposition by sputtering
71.20.Gj Other metals and alloys
78.20.Ls Magneto-optical effects

Subpicosecond Faraday effect in Cd1−xMnxTe and its application in magneto-optical sampling

R. Rey-de-Castro, D. Wang, X. Zheng, A. Verevkin, Roman Sobolewski, M. Mikulics, R. Adam, P. Kordoš, and A. Mycielski

Appl. Phys. Lett. 85, 3806 (2004); http://dx.doi.org/10.1063/1.1809280 (3 pages) | Cited 5 times

Online Publication Date: 29 October 2004

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We present our studies on a subpicosecond Faraday effect in diluted magnetic semiconducting Cd1−xMnxTe single crystals and its application in a magneto-optical (MO) sampling system for time-resolved detection of ultrafast current pulses. The measurements were performed at 10 K. We used the Cd0.38Mn0.62Te crystal as the active MO medium and a low-temperature-grown free-standing GaAs photoconductive switch integrated into a coplanar transmission line as the picosecond electrical pulse generator. We observed subpicosecond MO transients that correspond to the intrinsic MO low-temperature response in the Cd1−xMnxTe system with the high Mn concentration. The current sensitivity of our MO system was found to be ∼0.1 mA. We have demonstrated that the MO sampling technique using the Cd0.38Mn0.62Te transducer is as fast as the standard LiTaO3, electro-optical sampling technique and allows for a complementary (magnetic-field component) characterization of electrical picosecond transients in ultrafast switching devices. Observation of the subpicosecond Faraday effect in Cd1−xMnxTe crystals makes them very attractive for ultrafast optical modulators.
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81.05.Dz II-VI semiconductors
75.50.Pp Magnetic semiconductors
78.20.Ls Magneto-optical effects
78.47.-p Spectroscopy of solid state dynamics

Dependence of ferromagnetic properties on carrier transfer at GaMnN∕GaN:Mg interface

F. E. Arkun, M. J. Reed, E. A. Berkman, N. A. El-Masry, J. M. Zavada, M. L. Reed, and S. M. Bedair

Appl. Phys. Lett. 85, 3809 (2004); http://dx.doi.org/10.1063/1.1810216 (3 pages) | Cited 17 times

Online Publication Date: 29 October 2004

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We report on the dependence of ferromagnetic properties of metalorganic chemical vapor deposition grown GaMnN films on carrier transfer across adjacent layers. We found that the magnetic properties of GaMnN, as a part of GaMnN∕GaN:Mg heterostructures, depend on the thickness of both the GaMnN film and the adjacent GaN:Mg layer and on the presence of a wide band gap barrier at this interface. These results are explained based on the occupancy of the Mn energy band and how the occupancy can be altered due to carrier transfer at the GaMnN∕GaN:Mg interfaces.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
81.05.Ea III-V semiconductors
73.21.Ac Multilayers
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
75.30.Hx Magnetic impurity interactions
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.20.At Surface states, band structure, electron density of states
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.50.Dn Low-field transport and mobility; piezoresistance
61.72.S- Impurities in crystals

Giant exchange anisotropy observed in Mn–Ir∕Co–Fe bilayers containing ordered Mn3Ir phase

Ken-ichi Imakita, Masakiyo Tsunoda, and Migaku Takahashi

Appl. Phys. Lett. 85, 3812 (2004); http://dx.doi.org/10.1063/1.1812597 (3 pages) | Cited 26 times

Online Publication Date: 29 October 2004

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Exchange anisotropy of Mn73Ir27∕Co70Fe30 bilayers fabricated on a 50-nm-thick Cu under layer by changing the substrate temperature (Tsub) during the deposition of Mn–Ir layer was investigated, correlating with the crystallographic structure of Mn–Ir layer. The unidirectional anisotropy constant (JK) of the bilayers remarkably varied as a function of Tsub. After the thermal annealing of bilayers at 320 °C in a magnetic field of 1 kOe, JK steeply increased from 0.3 to 1.3 erg∕cm2, as Tsub was raised from room temperature to 170 °C. The blocking temperature was enhanced from 270 to 360 °C, simultaneously. The JK of 1.3 erg∕cm2 is nearly ten times larger than the values reported in Mn–Ir∕Co–Fe bilayers early in the research of them. The x-ray diffraction profiles showed that the ordered Mn3Ir phase was formed in the antiferromagnetic layer with increasing Tsub. From the coincidence of enhancing JK and increasing peak intensity of superlattice diffraction lines, the Mn3Ir phase was suggested to be an origin of the giant JK and the high blocking temperature.
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75.50.Ee Antiferromagnetics
75.50.Bb Fe and its alloys
68.55.A- Nucleation and growth
75.30.Gw Magnetic anisotropy
75.30.Et Exchange and superexchange interactions
81.15.Cd Deposition by sputtering
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.40.Gh Other heat and thermomechanical treatments

Origin of ferromagnetism in ZnO∕CoFe multilayers: Diluted magnetic semiconductor or clustering effect?

J. C. A. Huang, H. S. Hsu, Y. M. Hu, C. H. Lee, Y. H. Huang, and M. Z. Lin

Appl. Phys. Lett. 85, 3815 (2004); http://dx.doi.org/10.1063/1.1812844 (3 pages) | Cited 48 times

Online Publication Date: 29 October 2004

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Epitaxial growth of (0001) oriented [ZnO(20 math)∕Co0.7Fe0.3(x math)]25 multilayers (MLs) with nominal thickness x=1, 2 and 5 has been prepared on α-Al2O3 (0001) substrate by ion-beam sputtering. The magnetic properties over a temperature range of 6–350 K and structures probing by x-ray absorption spectroscopy (XAS) are reported. Above room-temperature ferromagnetism has been observed for x=1 and x=2 MLs, while superparamagnetic behavior dominates for x=5 ML. The field-cooled magnetization-temperature M(T) curves of x=1 and x=5 MLs can be fitted by a standard three-dimensional (3D) spin-wave and a Curie–Weiss model, respectively. For x=2 ML, however, neither a 3D spin-wave nor a Curie–Weiss model, but a combination of the two fits the M-T curve. The XAS studies together with the magnetic measurements further reveal that x=1 sample behaves as a diluted magnetic semiconductor (DMS) ML, while x=2 ML shows a mixed structure consisting of a minor component of DMS and a major component of CoFe clusters. A predominant clustering phase appears for x=5 ML.
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68.65.Ac Multilayers
73.21.Ac Multilayers
75.50.Pp Magnetic semiconductors
75.50.Bb Fe and its alloys
81.05.Dz II-VI semiconductors
75.20.En Metals and alloys
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
61.46.-w Structure of nanoscale materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.20.Ck Nonmetals
75.50.Dd Nonmetallic ferromagnetic materials
81.15.Cd Deposition by sputtering
81.15.Jj Ion and electron beam-assisted deposition; ion plating
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