Magnetic properties of Fe-base amorphous ultrafine particles

Sputter-etching an appropriate polymer substrate produces a densely-packed array of needlelike projections on the polymer surface. Rf sputter deposition of Fe
80
B
20
onto this surface produces an array of elongated finger-like projections of amorphous magnetic material, with diameters well under 1 μm and aspect ratios of 5 or more. These finger-like projections meet the definition of ultra-fine particles(UFP). Planar samples prepared in this way have a magnetic easy axis perpendicular to the sample surface with K
u
/2πM
s
²
=0.1-0.2, and have coercive fields up to 400 Oe. The dependence of magnetic properties on the sample morphology is described and discussed. Possible applications are briefly mentioned.