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Size effects on the magnetic properties of fine Fe-Cr particles |
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| Authors: | Y. Li W. Gong G.C. Hadjipanayis C.M. Sorensen K.J. Klabunde V. Papaefthymiou A. Kostikas A. Simopoulos |
| Affiliation: | a Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA b Departments of Physics, Kansas State University, Manhattan, KS 66506, USA c Departments of Chemistry, Kansas State University, Manhattan, KS 665, USA d University of Ioannina, 453 32, Ionnina, Greece e N.C.S.R. “Demokritos” 153 10 Ag., Paraskevi, Greece |
| Abstract: | The magnetic and structural properties of Fe1003−xCrx ultrafine particles with x = 5–20 have been studied as a function of particle size. Particles with a size in the range of 80–360 Å were prepared by gas evaporation under argon atmosphere. The particles with smaller diameter had a high coercivity at low temperatures and showed a stronger temperature dependence of coercivity. The x = 20 particles with a size 80 Å had a coercivity about 2100 Oe at 10 K with a superparamagnetic blocking temperature about 150 K. Mössbauer spectra showed the presence of Fe-Cr, -Fe and Fe-oxide components in the bigger particles, and Fe-Cr and Fe-oxides in the smaller particles. The coercivity at low temperatures increased with decreasing particle size and this was attributed to the higher percentage of Fe-oxide on the surface of the smaller particles. This interpretation was further supported by the temperature dependence of coercivity of Fe–Cr particles sandwiched between two Ag films. |
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