  To evaluate the self-heating effects of FeCo magnetic nanoparticles, the
surface oxidized FeCo nanoparticles were synthesized by co-precipitation method
with the reduction reaction without any post treatments. As-synthesized FeCo
nanoparticles exhibited the mean diameter of about 39 nm with the oxidized
shell thickness of about 4-5 nm. The saturation magnetization and coercivity
were obtained 172 emu/g and 268 Oe at 300 K, respectively. The heat elevation
of the FeCo magnetic colloid was measured under alternating magnetic fields of
76, 102, and 127 Oe with selectable frequencies of 190, 250 and 355 kHz. The
heat temperature increased up to about 45 oC from initial temperature of 24 oC
under 127 Oe and 355 kHz, which the specific absorption exhibited about 35.7
W/g.
