Magnetic ordering in Mg1+x Mn x Fe2−2x O4 system

Abstract

Magnetization measurements of the ferrite system Mg l+xMnxFe2_7~O 4 were undertaken primarily to study variation of the saturation magnetization with manganese concentration and to gain information about the type of magnetic ordering. The observations indicate the existence of Yafet-Kittel (YK) type of magnetic ordering in this system which is well supported by results of MiJssbaner effect measurements. A molecular field analysis of the YK spin ordering using the three-sublattice model is shown to explain the experimental data satisfactorily.

Localized canted spin behaviour in

“…The non-linear variation of lattice constant has been reported for the systems, which are not completely normal or inverse [14]. Similar results have been observed for the spinel systems: Mg 1þx Mn x Fe 2À2x O 4 [8], NiAl x Cr x Fe 2À2x O 4 [15] and CoCr x Fe 2À2x O 4 [16]. The non-linear variation of 'a' with x; can now be explained on the basis of distribution of cations among A-and B-sites.…”

“…2 shows the variation of n B with x: It is seen that the value of n B increases with Zn-content ðxÞ up to x ¼ 0:3; thereafter it decreases for further increase in Zn-concentration. Since the initial composition ðx ¼ 0:0Þ has been reported to have non-collinear spin ordering [8] it is not possible to explain the variation of n B as a function magnetic dilution (Zn-content) by using a naive collinear spin model suggested by Neel [18]. This can be corroborated with the following argument.…”

“…The X-ray diffraction patterns were indexed using a computer program and the values of lattice constant determined through NelsonRiley method [12]. The lattice constant of the initial composition x ¼ 0:0 has been reported [8] to be 0:8405 nm and in the present study it is found to be 0:8431 nm: The variation of lattice constant 'a' (nm) with content ðxÞ is shown in Fig. 1.…”

“…[4][5][6][7]. There is a report on non-collinear spin ordering in the spinel system Mg 1þx Mn x Fe 2À2x O 4 [8] but the data and argument presented by the authors does not seem cogent as it is based on the magnetization data recorded at 300 K where the T=T N ratio becomes extremely poor. It was thought worthwhile to undertake study of magnetic ordering in Zn 2þ substituted Mg 1:5 Mn 0:5 FeO 4 through magnetization measurements at 80 K; ðT=T N o0:2Þ:…”

“…The Y-K angle has been reported [8] for the initial composition Mg 1:5 Mn 0:5 FeO 4 to be 40 09 0 where the room-temperature ð300 KÞ magnetization data were used. The Neel temperature of this composition was also reported to be 470 K which gives very poor T=T N ratio B0:64 at T ¼ 300 K: Since the Y-K type of magnetic ordering is stable at low temperature, it is a good practice to calculate the canting angles at Tp77 K where T=T N o0:25: In the present work the canting angles have been calculated by using the mangetization data recorded at T ¼ 80 K:…”