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25 Jan 1999

Volume 74, Issue 4, pp. 483-629

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Fabrication of nanomagnet arrays by shadow deposition on self-organized semiconductor substrates

C. Teichert, J. Barthel, H. P. Oepen, and J. Kirschner

Appl. Phys. Lett. 74, 588 (1999); http://dx.doi.org/10.1063/1.123154 (3 pages) | Cited 19 times

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It is demonstrated how large-scale arrays of nanomagnets can be efficiently fabricated by shadow deposition onto faceted surfaces of self-organized Si1−xGex films. By pulsed laser deposition of Co in a grazing incidence geometry, we succeeded to cover just one selected type of facets resulting in isolated Co patches with an areal density of about 0.25×1012/in.2. These uniformly oriented nanomagnets have a parallelogram-shaped base with about 25 nm×35 nm edge lengths. Magneto-optic Kerr effect measurements reveal a clear in-plane anisotropy of the nanomagnets. © 1999 American Institute of Physics.
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75.50.Kj Amorphous and quasicrystalline magnetic materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Fg Pulsed laser ablation deposition
75.50.Cc Other ferromagnetic metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
78.20.Ls Magneto-optical effects

Isomagnetic reversal in sintered NdFeB

D. C. Crew, P. G. McCormick, and R. Street

Appl. Phys. Lett. 74, 591 (1999); http://dx.doi.org/10.1063/1.123155 (3 pages) | Cited 7 times

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Measurements of reversible and irreversible magnetization have been used to examine the reversal process on the initial magnetization curve in sintered NdFeB. It is found that the reversal process involves equal and opposite changes of irreversible and reversible magnetization, described here as isomagnetic reversal, resulting in no net change in magnetization during reversal. This result is consistent with the observation that magnetic viscosity is negligible on the initial magnetization curve. © 1999 American Institute of Physics.
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75.50.Ww Permanent magnets
75.50.Bb Fe and its alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Improvement in spin-wave resonance characteristics of epitaxial barium-ferrite thin films by using an aluminum-doped strontium-ferrite buffer layer

S. R. Shinde, S. E. Lofland, C. S. Ganpule, S. M. Bhagat, S. B. Ogale, R. Ramesh, and T. Venkatesan

Appl. Phys. Lett. 74, 594 (1999); http://dx.doi.org/10.1063/1.123156 (3 pages) | Cited 10 times

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We report on the effects of using SrFe7Al5O19 as a buffer layer for growth of high-quality epitaxial barium-ferrite thin films on sapphire substrates. X-ray diffraction studies reveal that the buffer layer causes the interfacial strains in the barium-ferrite films to relax. As a result, the ferromagnetic resonance linewidth decreases even in the as-deposited case. However, the more striking result is the drastic reduction in the linewidth that occurs when the barium-ferrite film is deposited on the buffer layer and subsequently annealed at 1000 °C for 2 h, allowing the observation of a large number of spin-wave resonances (up to the 15th mode), indicating an improvement in both the surface and interface characteristics. © 1999 American Institute of Physics.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.50.Gg Ferrimagnetics
75.70.Ak Magnetic properties of monolayers and thin films
68.60.Bs Mechanical and acoustical properties

Microstructure and magnetic properties of Sm2(Fe, Si)17Cx/α-Fe nanocomposite magnets prepared under high pressure

X. Y. Zhang, J. W. Zhang, W. K. Wang, W. Yu, J. H. Zhao, and Y. F. Xu

Appl. Phys. Lett. 74, 597 (1999); http://dx.doi.org/10.1063/1.123157 (3 pages) | Cited 19 times

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We present microstructure and magnetic properties of Sm2(Fe, Si)17Cx/α-Fe nanocomposite magnets prepared under a pressure of 4 GPa at a temperature of 923 K. A high-pressure experiment was carried out in a belt-type pressure apparatus. Analyses of x-ray diffraction and transmission electron microscopy show that the nanocomposite magnets have a grain size of 6–8 nm, which provides a strong exchange coupling between hard and soft magnetic phases. As a result, the magnets have, compared with nanocomposite magnets prepared under normal pressure, a significant increase in both coercivity, from 132 to 500 kA/m, and remanent magnetization, from 0.68 to 0.83Ms. © 1999 American Institute of Physics.
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75.50.Ww Permanent magnets
75.50.Vv High coercivity materials
61.72.-y Defects and impurities in crystals; microstructure
61.46.-w Structure of nanoscale materials
75.50.Kj Amorphous and quasicrystalline magnetic materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
62.50.-p High-pressure effects in solids and liquids
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys

Electrical noise in hysteretic ferromagnet–insulator–ferromagnet tunnel junctions

E. R. Nowak, M. B. Weissman, and S. S. P. Parkin

Appl. Phys. Lett. 74, 600 (1999); http://dx.doi.org/10.1063/1.123158 (3 pages) | Cited 8 times

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Low frequency noise has been measured in magnetic tunnel junctions that have Al2O3 tunnel barriers and magnetoresistance values up to 35% at 295 K. Fluctuations in voltage were found to cross over from Johnson noise to shot noise at low bias voltages, in quantitative agreement with theories of noise in quantum ballistic systems. 1/f resistance noise, where f is frequency, predominates at larger biases and is proportional to the mean current squared. This noise is attributed to trapping processes and it depends sensitively on the relative position of the oxide edge and the ferromagnet–Al interface. © 1999 American Institute of Physics.
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73.40.Rw Metal-insulator-metal structures
73.50.Td Noise processes and phenomena
73.40.Gk Tunneling
75.45.+j Macroscopic quantum phenomena in magnetic systems
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.50.Bb Fe and its alloys
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