We have synthesized a series of granular Fe‐SiO2 solids consisting of Fe metal granules of nanometer sizes embedded in an insulating SiO2 matrix. The ultrafine microstructures, revealed by TEM, are achieved by using a high‐rate magnetron sputtering system. The magnetic properties of such solids are determined by the granular size and the metal volume fraction. Below the percolation threshold, isolated single‐domain particles having large magnetic coercivity in the blocked state exhibit superparamagnetic relaxation, which has been studied by using SQUID magnetometry and Mössbauer spectroscopy. Above the percolation threshold, magnetic coercivity drops dramatically and the magnetic properties approach that of pure Fe. The anisotropy energy of the magnetic granules, much larger than that due to magnetocrystalline anisotropy, has been determined.

Topics
Magnetic properties, Superconducting quantum interference device, Magnetic anisotropy, Magnetron sputtering, Metal oxides, Mossbauer spectroscopy
1.
B. Abeles, in Applied Solid State Science: Advances in Materials and Device Research, edited by R. Wolfe (Academic, New York, 1976), p. 1.
2.
W. P.
Halperin
,
Rev. Mod. Phys.
58
,
533
(
1986
).
Google Scholar
Crossref
Search ADS
 
3.
G. R. Hoy, in Mossbauer Spectroscopy Applied to Inorganic Chemistry Vol. 1, edited by G. J. Lang (Plenum, New York, 1984), p. 195.
4.
I. S. Jacobs and C. P. Bean, in Magnetism III, edited by G. T. Rado and H. Suhl (Academic, New York, 1963), p. 275.
5.
S.
Morup
,
H.
Topsoe
, and
B. S.
Clausen
,
Phys. Scr.
25
,
713
(
1982
).
Google Scholar
Crossref
Search ADS
 
This content is only available via PDF.
© 1987 American Institute of Physics.
1987
American Institute of Physics
You do not currently have access to this content.