Magnetic properties and energy absorption of CoFe2O4 nanoparticles for   magnetic hyperthermia
  We have studied the magnetic and power absorption properties of three samples of CoFe2O4 nanoparticles with sizes from 5 to 12 nm prepared by thermal decomposition of Fe (acac)3 and Co(acac)2 at high temperatures. The blocking temperatures TB estimated from magnetization M(T) curves spanned the range 180 < TB < 320 K, reflecting the large magnetocrystalline anisotropy of these nanoparticles. Accordingly, high coercive fields HC \approx 1.4 - 1.7 T were observed at low temperatures. Specific Power Absorption (SPA) experiments carried out in ac magnetic fields indicated that, besides particle volume, the effective magnetic anisotropy is a key parameter determining the absorption efficiency. SPA values as high as 98 W/g were obtained for nanoparticles with average size of \approx12 nm. 
T.E. Torres, A.G. Roca, M.P. Morales, A. Ibarra, C. Marquina, M.R.   Ibarra and G.F. Goya
cond-mat.mtrl-sci physics.bio-ph physics.med-ph