Journal of Magnetism and Magnetic Materials 280 (2004) 23–30 Localized canted spin behaviour in Zn x Mg 1:5x Mn 0:5 FeO 4 spinel ferrite system K.P. Thummer, M.C. Chhantbar, K.B. Modi*, G.J. Baldha, H.H. Joshi Department of Physics, Saurashtra University, Rajkot 360005, India Received 20 August 2003; received in revised form 11 November 2003 Abstract The structural and bulk magnetic properties of the spinel system Zn x Mg 1:5x Mn 0:5 FeO 4 with x ¼ 0:0–0.6 have been investigated by means of X-ray diffraction, magnetization and AC susceptibility measurements. The distribution of the cations has been deduced through XRD intensity analysis and the non-linear variation of lattice constant with Zn- contenthasbeenexplainedonthebasisofdistributionofthecations.Thethreesublatticemodelsanalysisofthesystem basedontheuniformandlocalizedspincantingapproachhavebeenusedtoexplainthevariationofmagnetizationwith Zn-concentration. The Neel temperature obtained from thermal variation AC susceptibility measurements decreases with Zn-content ðxÞ: r 2004 Elsevier B.V. All rights reserved. Keywords: Ferrites; Cation distribution; Magnetization; Canted spin structure; AC susceptibility 1. Introduction It is well known that when ferrites are suffi- ciently diluted with non-magnetic atoms they can show a wide spectrum of magnetic order ranging from ferrimagnetism, antiferromagnetism, local canted spin (LCS) to semi-spin glass and spin glass [1]. This is due to the fact that in spinel ferrites all the three exchange interactions viz. J AA ; J AB and J BB are negative and |J AB jXjJ BB jXjJ AA j; as a result there are unsatisfied bonds in the ferrimagnetic phase, increasing the magnetic dilu- tion emphasize the competition between the different exchange interactions results in a variety of magnetic orders [1]. A quantitative phase diagram was proposed by Villain [2] that predicts ferrimagnetic, semi-spin glass, spin glass ground states as the magnetic dilution progresses. The presence of Fe 2þ ; Co 2þ or Mn 3þ ions in ferrite systems introduces an additional factor i.e. uni- axial random anisotropy [3], which may compli- cate the magnetic phase diagram. The magnesium ferrite ðMgFe 2 O 4 Þ; a partially inverse spinel has been studied for structural and magnetic properties with non-magnetic substitu- tions, such as Ti 4þ ; Zr 4þ ; Zn 2þ ; Al 3þ ; etc. [4–7]. There is a report on non-collinear spin ordering in the spinel system Mg 1þx Mn x Fe 22x O 4 [8] but the data and argument presented by the authors does notseemcogentasitisbasedonthemagnetization data recorded at 300 K where the T =T N ratio becomes extremely poor. It was thought worth- while to undertake study of magnetic ordering in Zn 2þ substituted Mg 1:5 Mn 0:5 FeO 4 through mag- netization measurements at 80 K; ðT =T N o0:2Þ: ARTICLE IN PRESS *Corresponding author. Tel.: +91-281-257-8505x403. E-mail address: kunalbmodi2003@yahoo.com (K.B. Modi). 0304-8853/$-see front matter r 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2004.02.017