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18 Jan 1999

Volume 74, Issue 3, pp. 329-478

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Magnetic dissipation microscopy in ambient conditions

Roger Proksch, Ken Babcock, and Jason Cleveland

Appl. Phys. Lett. 74, 419 (1999); http://dx.doi.org/10.1063/1.123047 (3 pages) | Cited 9 times

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We have quantified sub-picowatt power losses in very soft (yttrium iron garnets) and relatively hard (metal evaporated tape) ferromagnetic materials associated with dissipative micromagnetic processes during magnetic force microscope imaging. We had a thermally limited power resolution of 2×10−15 W in a 1 kHz bandwidth operating in air. In the epitaxial garnet film, peak dissipation (3×10−13 W) was spatially correlated with domain wall motion induced by the localized field from the tip. In metal-evaporated recording tape imaged with a cantilever coated with 50 nm of CoCr, the dissipation was observed in extremely localized regions of the sample (<10 nm). Absence of dissipation features when using a different tip suggests the dissipation originated in the tip rather than the sample. This technique shows promise for mapping micromagnetic structure and dissipative processes, quantitatively evaluating magnetic force microscope (MFM) tip performance, and for detecting perturbations in MFM images. © 1999 American Institute of Physics.
Show PACS
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
07.79.Pk Magnetic force microscopes
75.70.Ak Magnetic properties of monolayers and thin films

Micromagnetics and magnetoresistance of a Permalloy point contact

R. P. van Gorkom, J. Caro, S. J. C. H. Theeuwen, K. P. Wellock, N. N. Gribov, and S. Radelaar

Appl. Phys. Lett. 74, 422 (1999); http://dx.doi.org/10.1063/1.123048 (3 pages) | Cited 21 times

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We performed micromagnetic calculations for a Permalloy point contact. The magnetization configurations show the formation of a Néel wall in the constriction. The occurrence of a Néel wall instead of a Bloch wall results from the dipole–dipole energy in this region. The evolution of the magnetization with field differs strongly for fields parallel and perpendicular to the electrodes. In the former case, the pattern evolves abruptly and in a narrow range, while in the latter case it evolves smoothly and in a rather wide range. From the magnetization patterns, we estimate the domain-wall magnetoresistance and the anisotropic magnetoresistance, which we compare with experimental data. © 1999 American Institute of Physics.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.40.Jn Metal-to-metal contacts
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure

Suppression of the face-centered-cubic-hexagonal-close-packed stacking fault in Co/Cu(111) ultrathin films by pulsed laser deposition

M. Zheng, J. Shen, Ch. V. Mohan, P. Ohresser, J. Barthel, and J. Kirschner

Appl. Phys. Lett. 74, 425 (1999); http://dx.doi.org/10.1063/1.123049 (3 pages) | Cited 15 times

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The thermal deposition of Co onto Cu(111) results in three-dimensional island growth and a face-centered-cubic-hexagonal-close-packed stacking fault, which hinders a complete antiferromagnetic coupling in Co/Cu(111) superlattices. We report that Co/Cu(111) films can be grown with good layer-by-layer morphology and significantly less stacking faults by pulsed laser deposition. We show that a complete antiferromagnetic coupling can be achieved in the pulsed laser deposited Co/Cu trilayer. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.Nn Stacking faults and other planar or extended defects
81.15.Fg Pulsed laser ablation deposition

Longitudinal magnetoresistance of CrO2 thin films

Katsuhiko Suzuki and P. M. Tedrow

Appl. Phys. Lett. 74, 428 (1999); http://dx.doi.org/10.1063/1.123050 (2 pages) | Cited 26 times

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The longitudinal magnetoresistance (LMR) of thin films of the putative half-metallic ferromagnet CrO2 deposited by chemical vapor deposition onto TiO2/Si(111) substrates has been measured in the temperature range 0.55 K<T<4.2 K in magnetic fields up to 7 T. The dependence of the LMR on small changes in the angle between the applied field and the substrate plane was also measured at T=1.3 K. X-ray diffraction measurements showed that these films have a textured rutile structure with a axis and 〈110〉 orientations normal to the substrates. The LMR of these films at about 3 T was about twice that of similar films that showed only a 〈100〉 orientation normal to their ZrO2 substrates. A change in the substrate orientation relative to the applied field direction of 10° caused a 25% decrease in the magnitude of the LMR at 3 T. The results suggest that the existence of the 〈110〉 crystallite structure strongly affects the magnetoresistance. © 1999 American Institute of Physics.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.61.At Metal and metallic alloys
75.50.Cc Other ferromagnetic metals and alloys
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films

Sm(Co, Cu, Ni) thin films with giant coercivity

C. Prados and G. C. Hadjipanayis

Appl. Phys. Lett. 74, 430 (1999); http://dx.doi.org/10.1063/1.123051 (3 pages) | Cited 7 times

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Nanostructured Sm(Co, Ni, Cu) thin films have been obtained by heat treating as-deposited sputtered amorphous films. The room-temperature coercivity increases from less than 100 Oe in the amorphous state to 42 kOe in a SmCo2Cu3 sample annealed 30 min at 550 °C. Structural data in the optimum samples suggest a particle size around 10 mn. Magnetic viscosity measurements indicated that the switching volume is of the same order as the crystallite size. Remanence measurements showed that interparticulate interactions are magnetizing and rather independent of the crystallization stage. These data indicate that the huge coercivity enhancement is due to domain-wall pinning at high anisotropy Sm–Co precipitates. © 1999 American Institute of Physics.
Show PACS
75.50.Vv High coercivity materials
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
81.40.Rs Electrical and magnetic properties related to treatment conditions

Hotspot mixing: A framework for heterodyne mixing in superconducting hot-electron bolometers

D. Wilms Floet, E. Miedema, T. M. Klapwijk, and J. R. Gao

Appl. Phys. Lett. 74, 433 (1999); http://dx.doi.org/10.1063/1.123052 (3 pages) | Cited 34 times

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We propose a framework to interpret heterodyne mixing in superconducting hot-electron bolometers. The physical conversion process of the mixer is the result of an electronic hotspot, of which the length, and consequently the resistance, oscillates at the intermediate frequency. On the basis of this concept, we calculate the (un)pumped current–voltage relation, the dc voltage responsivity, and the mixer conversion efficiency. © 1999 American Institute of Physics.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
85.25.Cp Josephson devices
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