Enhanced Néel temperature in Mn ferrite nanoparticles linked to growth-rate-induced cation inversion.
Mn ferrite (MnFe(2)O(4)) nanoparticles, having diameters from 4 to 50 nm, were synthesized using a modified co-precipitation technique in which mixed metal chloride solutions were added to different concentrations of boiling NaOH solutions to control particle growth rate. Thermomagnetization measurements indicated an increase in Néel temperature corresponding to increased particle growth rate and particle size. The Néel temperature is also found to increase inversely proportionally to the cation inversion parameter, delta, appearing in the formula (Mn(1-delta)Fe(delta))(tet)[Mn(delta)Fe(2-delta)](oct)O(4). These results contradict previously published reports of trends between Néel temperature and particle size, and demonstrate the dominance of cation inversion in determining the strength of superexchange interactions and subsequently Néel temperature in ferrite systems. The particle surface chemistry, structure, and magnetic spin configuration play secondary roles.
Yang
Aria
A
Center for Microwave Magnetic Materials and Integrated Circuits, Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA.
Chinnasamy
C N
CN
Greneche
J M
JM
Chen
Yajie
Y
Yoon
Soack D
SD
Chen
Zhaohui
Z
Hsu
Kailin
K
Cai
Zhuhua
Z
Ziemer
Kate
K
Vittoria
C
C
Harris
V G
VG
D002412:Cations; D003460:Crystallization / Q000379:methods*; D005590:Fractional Precipitation; D046911:Macromolecular Substances / Q000737:chemistry; D008345:Manganese / Q000737:chemistry*; D008422:Materials Testing; D008968:Molecular Conformation; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D013499:Surface Properties; D013696:Temperature
D002412:Cations; D046911:Macromolecular Substances; D008345:Manganese