T J Jackson et al 2000 J. Phys.: Condens. Matter 12 1399 doi:10.1088/0953-8984/12/7/321
Superparamagnetic relaxation in iron nanoclusters measured by low energy muon spin rotation
T J Jackson
, C Binns
, E M Forgan, E Morenzoni§, Ch Niedermayer||, H Glückler§, A Hofer, H Luetkens, T Prokscha§, T M Riseman, A Schatz, M Birke, J Litterst¶, G Schatz|| and H P Weber§
Low energy (16 keV) muons were used to probe the dynamic magnetic behaviour of iron nanoclusters embedded in a silver thin film matrix. The silver film was 500 nm thick and contained a volume fraction of 0.1% iron. Measurements were made in a field of 25 mT, applied normal to the plane of the film, in the temperature range 4.7 K to 300 K. At temperatures above 20 K thermal activation of the cluster moments was seen as a narrowing of the field distribution sensed by the implanted muons. An intrinsic cluster relaxation time of τ0 = 12 ± 4 ns and an activation energy of 51 ± 9 K were deduced from fits to the data. SQUID magnetometry of thicker (1.5 µm) but otherwise identical films on graphite substrates showed the clusters to have a volume of the order of 10-26 m3, from which a cubic anisotropy constant of K = 2.3 ± 0.4 × 105 J m-3 was calculated. Remanence measurements showed no evidence of a preferred orientation for the magnetization of the cluster assembly.
- PACS
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68.55.-a Thin film structure and morphology
76.75.+i Muon spin rotation and relaxation
75.75.+a Magnetic properties of nanostructures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
- Subjects
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Condensed matter: electrical, magnetic and optical
- Dates
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Issue 7 (21 February 2000)
Received 25 November 1999
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Superparamagnetic relaxation in iron nanoclusters measured by low energy muon spin rotation
T J Jackson et al 2000 J. Phys.: Condens. Matter 12 1399
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