Neel temperature enhamcement in nanostructured nickel zinc ferrite

The Neel temperature of Ni<SUB>0.5</SUB>Zn<SUB>0.5</SUB>Fe<SUB>2</SUB>O<SUB>4 </SUB>spinel ferrite increases significantly from 538 K in the bulk state to 592 K when the grain size is reduced to 16 nm by milling in a high-energy ball mill. This has been attributed to an increase in the AB superexchange interaction strength due to a possible enhancement in the magnetic ion concentration in the A-site on milling, as is evident from extended x-ray absorption fine structure and in-field M&#214;ssbauer measurements