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

摘要

Monodispersed ferrite nanoparticles of Fe_3O_4, MnFe_2O_4, and CoFe_2O_4 (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 v =10 kHz, MnFe_2O_4 exhibits the single-peak maximum of loss with the value of 273 erg/s • g at T= 65 K, whereas for the CoFe_2O_4, a maximum of 132 erg/s • g (T=217 K) was determined. A considerable drop in the efficiency was determined for the Fe_3O_4 nanoparticles, with the value of 20 erg/s·g at T = 43.5 K.