Tuning the thermal relaxation of transition-metal ferrite nanoparticles through their intrinsic magnetocrystalline anisotropy

Monodispersed ferrite nanoparticles of Fe3O4, MnFe2O4, and CoFe2O4 (near to 10 nm), were synthesized by organometallic synthesis, showing the same homogeneous chemical, morphological, and crystalline characteristics. The study and correlation of the thermal relaxation processes were analyzed through static and dynamic measurements. Due to the intrinsic chemical characteristics and magnetocrystalline anisotropy of the ferrite nanoparticles, the energy barrier can be tuned to a range between 1100 K <= E-B <= 7300 K, showing an alternative approach for tuning the magnetic dynamic properties, in contrast to the well-known mechanism through particle-size-effects. Specific loss power efficiencies were evaluated for the three ferrite samples. Comparing the three samples at the maximum ac frequency of nu = 10 kHz, MnFe2O4 exhibits the single-peak maximum of loss with the value of 273 erg/s . g at T = 65 K, whereas for the CoFe2O4, a maximum of 132 erg/s . g (T = 217 K) was determined. A considerable drop in the efficiency was determined for the Fe3O4 nanoparticles, with the value of 20 erg/s . g at T = 43.5 K. (C) 2011 American Institute of Physics. [doi:10.1063/1.3638053]