Nanocrystalline/nanosized manganese substituted nickel ferrites – Ni1−xMnxFe2O4 obtained by ceramic-mechanical milling route

Abstract

Manganese substituted nickel ferrites, Ni1−xMnxFe2O4 (x=0, 0.3, 0.5 and 0.7) have been obtained by a combined method, heat treatment and subsequent mechanical milling. The samples were characterised by X-ray diffraction, differential scanning calorimetry and magnetic measurements. The increase of the Mn2+ cations amount into the spinel structure leads to a significant expansion of the cubic spinel structure lattice parameter. The crystallite size decreases with increasing milling time up to 120min, more rapidly for the nickel–manganese ferrites with a large amount of Mn2+ cations (x=0.7). After only 15min of milling the mean crystallites size is less than 25nm for all synthesised ferrites. The Néel temperature decreases by increasing Mn2+ cation amount from 585°C for x=0 up to 380°C for x=0.7. The magnetisation of the ferrite increases by introducing more manganese cations into the spinel structure. The magnetisation of the milled samples decreases by increasing milling time for each ratio among Ni and Mn cations and tends to be difficult to saturate, a behaviour assigned to the spin canted effect.