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2 Aug 2004

Volume 85, Issue 5, pp. 701-848

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 807 (2004); http://dx.doi.org/10.1063/1.1777817 (3 pages)

Henry J. Liu and Kyeongjae Cho
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High-temperature ferromagnetism in manganese-doped indium–tin oxide films

John Philip, Nikoleta Theodoropoulou, Geetha Berera, Jagadeesh S. Moodera, and Biswarup Satpati

Appl. Phys. Lett. 85, 777 (2004); http://dx.doi.org/10.1063/1.1773617 (3 pages) | Cited 60 times

Online Publication Date: 27 July 2004

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High-temperature ferromagnetism is demonstrated in Mn-doped indium–tin oxide (ITO) films deposited using reactive thermal evaporation. These films were grown on sapphire (0001), Si∕SiO2 as well as Si (100) substrates with the highest magnetic moment observed around 0.8 μB∕Mn in 5% Mn-doped ITO films. The electrical conduction is n type and the carrier concentration is ∼2.5×1019 cm−3 for 5% Mn doping. An anomalous Hall effect is observed in magnetotransport measurements, showing that the charge carriers are spin polarized, revealing the magnetic interaction between itinerant electrons and localized Mn spins. The carrier concentration can be varied independent of the Mn concentration in this transparent ferromagnetic semiconductor for its easy integration into magneto-optoelectronic devices.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
68.55.A- Nucleation and growth
75.70.Ak Magnetic properties of monolayers and thin films
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.My Galvanomagnetic and other magnetotransport effects
75.30.Cr Saturation moments and magnetic susceptibilities
75.47.Lx Magnetic oxides
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Room-temperature magneto-optical activity of InMnAs thin films

P. T. Chiu, S. J. May, and B. W. Wessels

Appl. Phys. Lett. 85, 780 (2004); http://dx.doi.org/10.1063/1.1773618 (3 pages) | Cited 5 times

Online Publication Date: 27 July 2004

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Room-temperature magneto-optical activity of In1−xMnxAs heteroepitaxial thin films grown on InAs (001) and GaAs (001) substrates has been studied using the longitudinal magneto-optical Kerr effect. For single-phase layers grown on InAs and GaAs with x ranging from 0.03 to 0.09, square hysteresis loops that indicate ferromagnetic order were observed. The magnitude of the saturation Kerr rotation of all the InMnAs samples ranged from 0.29 to 1.1 mdeg, and scaled with the manganese concentration. The shape of the hysteresis curves for samples of InMnAs grown GaAs was invariant with respect to rotation about the sample normal, indicating in-plane magnetic isotropy. In contrast, InMnAs layers on InAs exhibited strong uniaxial in-plane anisotropy with the easy axis of magnetization along the [110] and [mathmath0] directions. The magnetic anisotropy is attributed to the effect of epitaxial strain.
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75.50.Pp Magnetic semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
68.55.A- Nucleation and growth
78.20.Ls Magneto-optical effects
75.30.Gw Magnetic anisotropy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Enhancement of the Curie temperature in GaMnAs∕InGaMnAs superlattices

A. Koeder, W. Limmer, S. Frank, W. Schoch, V. Avrutin, R. Sauer, A. Waag, K. Zuern, and P. Ziemann

Appl. Phys. Lett. 85, 783 (2004); http://dx.doi.org/10.1063/1.1771802 (3 pages) | Cited 3 times

Online Publication Date: 27 July 2004

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We report on an enhancement of the Curie temperature in GaMnAs∕InGaMnAs superlattices grown by low-temperature molecular beam epitaxy which is due to thin InGaMnAs or InGaAs films embedded into the GaMnAs layers. The pronounced increase of the Curie temperature is strongly correlated to the In concentration in the embedded layers. Curie temperatures up to 110 K are observed in such structures compared to 60 K in GaMnAs single layers grown under the same conditions. A further increase in TC up to 130 K can be achieved using postgrowth annealing at temperatures near the growth temperature. Pronounced thickness fringes in the high-resolution x-ray diffraction spectra indicate good crystalline quality and sharp interfaces in the structures.
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75.50.Pp Magnetic semiconductors
68.65.Cd Superlattices
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments

Investigation on the magnetic and electrical properties of crystalline Mn0.05Si0.95 films

F. M. Zhang, X. C. Liu, J. Gao, X. S. Wu, Y. W. Du, H. Zhu, J. Q. Xiao, and P. Chen

Appl. Phys. Lett. 85, 786 (2004); http://dx.doi.org/10.1063/1.1775886 (3 pages) | Cited 66 times

Online Publication Date: 27 July 2004

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The magnetic and electrical properties of crystalline Mn0.05Si0.95 films prepared by post-thermal treatment of the as-deposited amorphous Si-Mn (95 at.%−5 at.%) have been investigated. Both the temperature dependence and field dependence of magnetization were measured using superconducting quantum interference devices, and it has been indicated that the film materials are ferromagnetic with Curie temperature over 400 K. X-ray diffraction analysis revealed full crystallization of the films and the incorporation of Mn into the host crystalline Si lattice. Behavior of thermally activated conduction processes of the films has been evinced by electrical property measurement for the films.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
73.61.Jc Amorphous semiconductors; glasses
81.05.Gc Amorphous semiconductors
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
64.70.K- Solid-solid transitions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Rapidly solidified (FePt)70P30 alloy with high coercivity

A. A. Kündig, N. Abe, M. Ohnuma, T. Ohkubo, H. Mamiya, and K. Hono

Appl. Phys. Lett. 85, 789 (2004); http://dx.doi.org/10.1063/1.1776333 (3 pages) | Cited 11 times

Online Publication Date: 27 July 2004

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The alloy Fe35Pt35P30, whose composition is close to a ternary eutectic, was rapidly solidified by melt spinning and the ribbon exhibited a high coercivity, exceeding 20 kOe after annealing. The alloy was mainly composed of L10 ordered FePt and PtP2 with an average grain size of about 50 nm. In the as-cast state, the alloy was comprised of about 20-nm-diam FePt and PtP2 grains supersaturated with P and Fe, respectively, and the coercivity was only 150 Oe. The high coercivity obtained following annealing is discussed on the basis of the microstructural observations.
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75.50.Bb Fe and its alloys
81.05.Bx Metals, semimetals, and alloys
81.30.Fb Solidification
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Vv High coercivity materials
81.40.Gh Other heat and thermomechanical treatments

Tailoring magnetic properties of core∕shell nanoparticles

Hao Zeng, Shouheng Sun, J. Li, Z. L. Wang, and J. P. Liu

Appl. Phys. Lett. 85, 792 (2004); http://dx.doi.org/10.1063/1.1776632 (3 pages) | Cited 50 times

Online Publication Date: 27 July 2004

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Bimagnetic FePt∕MFe2O4(M=Fe,Co) core∕shell nanoparticles are synthesized via high-temperature solution phase coating of 3.5 nm FePt core with MFe2O4 shell. The thickness of the shell is controlled from 0.5 to 3 nm. An assembly of the core∕shell nanoparticles shows a smooth magnetization transition under an external field, indicating effective exchange coupling between the FePt core and the oxide shell. The coercivity of the FePt∕Fe3O4 particles depends on the volume ratio of the hard and soft phases, consistent with previous theoretical predictions. These bimagnetic core∕shell nanoparticles represent a class of nanostructured magnetic materials with their properties tunable by varying the chemical composition and thickness of the coating materials.
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75.50.Cc Other ferromagnetic metals and alloys
81.07.Wx Nanopowders
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Et Exchange and superexchange interactions
61.46.-w Structure of nanoscale materials
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