Anomalous behaviour of cobalt in soft lithium-zinc ferrites

Mössbauer and magnetic studies of cobalt substituted lithium zinc ferrites prepared by citrate precursor method

“…An initial increase with cobalt concentration was observed and the value then decreases. Similar observation has been reported by other workers [5,18]. In ferrites the contribution to the magnetic moment comes mainly from the parallel uncompensated electron spin of individual ion.…”

“…As can be seen from Table 2 is thus expected to be strictly more magnetic with substitution. The observation of constant H A may indicate suppression of the effectiveness of Co 2+ substitution in presence of larger zinc concentration [5].…”

“…Co 2+ enters both A site and B sites. However for low concentration Co 2+ ion can be taken to be all in B site and at higher concentration a small amount was observed to go to the A sites [5,11,12]. Hence for small concentration of Co 2+ A site preference can be neglected and the cationic distribution can therefore be assumed to be where parenthesis and square brackets represent tetrahedral (A) and octahedral (B) sites, respectively.…”

“…This somewhat contradicts previous reports where it continuously increases with cobalt substitution. The decrease beyond x = 0.02 may indicate presence of canting and relaxation of Co 2+ and the suppression of effect of Co 2+ ions when substituted in presence of Zn ions in lithium ferrites [5,18].…”

“…Different methods have been proposed and citrate precursor method is one which is gaining importance while preparing fine grained ferrite powders for suitable purposes [1][2][3]. Lithium ferrite substituted with zinc has gained importance as it possess high saturation magnetization which is found to be useful in microwave communication and memory core applications [4][5][6]. Zinc substituted lithium ferrites has been observed to have highest saturation magnetization at nearly Zn = 0.2 [7][8][9].…”