Abstract
Ultrafine magnetic particles consisting of a metastable
iron-mercury alloy in Hg have been investigated by Mossbauer
spectroscopy and magnetization measurements. It was found that the
magnetic particles interact strongly, and around 100 K there is a
transition from a superparamagnetic state to a state in which the
magnetic moments of the particles are ordered. The magnetic
entropy change induced by application of a magnetic field was
determined in the temperature range from 70 to 200 K. When the
sample was magnetized in 1 T the magnetic entropy change was
almost constant in the temperature range from 130 to 200 K. In an
applied field of 0.1 T, the entropy change was lower, and
decreased with increasing temperature in the same temperature
range. A model which takes into account the magnetic interactions
between the particles was found to give a better description of
the magnetic entropy change than a model for non-interacting
superparamagnetic particles.
| Original language | English |
|---|---|
| Journal | Journal of Physics Condensed Matter |
| Volume | 9 |
| Pages (from-to) | 7173-7188 |
| ISSN | 0953-8984 |
| Publication status | Published - 1997 |