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18 Feb 2002

Volume 80, Issue 7, pp. 1111-1310

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Role of boron on grain sizes and magnetic correlation lengths in recording media as determined by soft x-ray scattering

Olav Hellwig, D. T. Margulies, B. Lengsfield, Eric E. Fullerton, and J. B. Kortright

Appl. Phys. Lett. 80, 1234 (2002); http://dx.doi.org/10.1063/1.1448665 (3 pages) | Cited 14 times

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We have measured the chemical grain sizes and magnetic correlation lengths in CoCr-based magnetic recording media films using resonant soft x-ray small-angle scattering. We find that the addition of boron, while leading to slightly smaller physical grains, dramatically reduces the magnetic correlation length. These results show that B additions effectively act to suppress intergranular magnetic exchange via segregation to the grain boundaries. © 2002 American Institute of Physics.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
68.55.-a Thin film structure and morphology
75.50.Ss Magnetic recording materials
75.50.Cc Other ferromagnetic metals and alloys
78.70.Ck X-ray scattering
75.30.Et Exchange and superexchange interactions
61.72.Mm Grain and twin boundaries
64.75.-g Phase equilibria

Magnetic CdSe-based quantum dots grown on Mn-passivated ZnSe

L. V. Titova, J. K. Furdyna, M. Dobrowolska, S. Lee, T. Topuria, P. Moeck, and N. D. Browning

Appl. Phys. Lett. 80, 1237 (2002); http://dx.doi.org/10.1063/1.1450254 (3 pages) | Cited 15 times

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In this letter we describe the properties of self-assembled CdSe quantum dots (QDs) grown on Mn-passivated ZnSe buffers. We show that the Mn deposited on the ZnSe surface during the passivation process acts as a nucleating seed for self-assembled QD formation. For moderate amounts of Mn deposition, the dots grown in this way show a significant improvement in size uniformity compared to CdSe dots grown on ZnSe without Mn passivation. Using photoluminescence, we also show that the dots exhibit large Zeeman splitting, indicating that this growth method is suitable for fabricating magnetic QDs that exhibit strong spin polarization effects. © 2002 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.65.Rv Passivation
68.65.Hb Quantum dots (patterned in quantum wells)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Pp Magnetic semiconductors
78.55.Et II-VI semiconductors
78.67.Hc Quantum dots
78.20.Ls Magneto-optical effects

Efficient electrical spin injection from a magnetic metal/tunnel barrier contact into a semiconductor

A. T. Hanbicki, B. T. Jonker, G. Itskos, G. Kioseoglou, and A. Petrou

Appl. Phys. Lett. 80, 1240 (2002); http://dx.doi.org/10.1063/1.1449530 (3 pages) | Cited 372 times

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We report electrical spin injection from a ferromagnetic metal contact into a semiconductor light emitting diode structure with an injection efficiency of 30% which persists to room temperature. The Schottky barrier formed at the Fe/AlGaAs interface provides a natural tunnel barrier for injection of spin polarized electrons under reverse bias. These carriers radiatively recombine, emitting circularly polarized light, and the quantum selection rules relating the optical and carrier spin polarizations provide a quantitative, model-independent measure of injection efficiency. This demonstrates that spin injecting contacts can be formed using a widely employed contact methodology, providing a ready pathway for the integration of spin transport into semiconductor processing technology. © 2002 American Institute of Physics.
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72.25.Mk Spin transport through interfaces
73.40.Ns Metal-nonmetal contacts
85.60.Jb Light-emitting devices
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
73.61.Ey III-V semiconductors
73.61.At Metal and metallic alloys
73.40.Gk Tunneling
75.50.Bb Fe and its alloys
75.70.Ak Magnetic properties of monolayers and thin films

Fast development of high coercivity in melt-spun Sm(Co,Fe,Cu,Zr)z magnets

A. Yan, A. Bollero, K. H. Müller, and O. Gutfleisch

Appl. Phys. Lett. 80, 1243 (2002); http://dx.doi.org/10.1063/1.1450253 (3 pages) | Cited 23 times

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A simple method was developed for magnetic hardening melt-spun Sm(Co,Fe,Cu,Zr)z alloys. The as-spun ribbons reached a coercivity of 2.8 T only by slow cooling from 850 to 400 °C, without the standard solid solution and isothermal aging treatments which are required for a bulk precipitation hardened 2:17 SmCo alloy. A single 1:7 phase, identical to that found in as-solubilized ribbons, was obtained in the as-spun state. At the same time, Cu and Zr are supersaturately dissolved in the 1:7 matrix by melt spinning due to its very high cooling rate. Thus, solid solution treatment can be avoided for melt-spun materials. After aging, more lamellar phase with larger width was observed by transmission electron microscope in ribbons without treatment in solution. This leads to faster development of a uniform finer cellular microstructure with a Cu-rich 1:5 cell boundary phase, which gives rise to stronger domain-wall pinning and therefore to higher coercivity. © 2002 American Institute of Physics.
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75.50.Ww Permanent magnets
07.55.Db Generation of magnetic fields; magnets
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure

Approach to saturation in nanomagnetic systems: Easy axis distribution and interactions

R. Iglesias and H. Rubio

Appl. Phys. Lett. 80, 1246 (2002); http://dx.doi.org/10.1063/1.1447600 (3 pages) | Cited 1 time

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Using the applied field angle dependence of the approach to saturation of the magnetization, a theory for the determination of the distribution of easy axes of anisotropy and the ratio between interaction and anisotropy in bidimensional nanomagnetic materials is proposed. The usual saturation process laws in two dimensions at high and intermediate field ranges are recovered and other dependencies between the former are found and justified in terms of scaling arguments. Finally, an approximate analytical model that provides a simpler method by which to determine the easy axis distribution and interaction strength is discussed. © 2002 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
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