Large tunability of Neel temperature by growth-rate-induced cation inversion in Mn-ferrite nanoparticles

摘要

The tuning of Neel temperature by greater than 100 K in nanoparticle Mn-ferrite was demonstrated by a growth-rate-induced cation inversion. Mn-ferrite nanoparticles, having diameters from 4 to 50 nm, were synthesized via coprecipitation synthesis. The Neel temperature (T_N) increased inversely to the cation inversion parameter, 8 (i.e., defined as (Mn_(1-δ)Fe_δ)~(tet)[Mn_δFe_(2-δ)]~(oct)O_4). Concomitantly, T_N increased with increased particle growth rate and particle size. These results unambiguously establish cation inversion as the dominant mechanism in modifying the superexchange leading to enhanced T_N. The ability to tailor T_N enables greater flexibility in applying nanoparticle ferrites in emerging technologies.