Solid State Communications, Vol. 68, No. 6, pp. 549-554, 1988. 0038-1098/88 $3.00 + .00 Printed in Great Britain. Pergamon Press plc EFFECT OF Ti 4~ SUBSTITUTION ON THE HYPERFINE INTERACTIONS IN LiZn FERRITES Sumitra Phanjoubam, Deepika Kothari and J.S. Baijal* Department of Physics and Astrophysics, University of Delhi, Delhi-110 007, India and Pran Kishan Solid State Physics Laboratory, Lucknow Road, Delhi-110 007, India (Received 24 February 1988 by P. Wachter) 57 Fe M6ssbauer investigations were made on the system Li0.35 ~0.5,Zn0.3- Ti, Fc, 35 r.~,O4(0.0 ~< t ~< 1.2) at 300K and 77K. The effect of vari- ation of Ti concentration on the various hyperfine interactions have been discussed. It is observed that for t ~< 0.6 the M6ssbauer spectra show well defined Zeeman pattern. The spectra for t = 0.8 is relaxed while for t >/ 1.0 there is the existence of a central doublet along with thc relaxed magnetic sextet. This anomalous behaviour of the M6ssbauer spectra at high diamagnetic substitution and the origin of the central doublct havc been discussed. I. INTRODUCTION LITHIUM FERRITES are known to possess an attractive set of properties like high Curie temperature, rectangular hysteresis loop, low stress sensitivity and low microwave dielectric losses. These properties have made them find extensive use in industrial, tech- nological and microwave applications. The properties of these ferrites are very sensitive to the method of preparation and the type and amount of impurity substitution. The influence of a number of substi- tutions have been studied to obtain a high quality ferrite for a specific application. Titanium and zinc are the most commonly used dopants and they modify the saturation magnetization for microwave appli- cations. Such diamagnetically substituted lithium ferrites have been the subject of investigation by. a number of workers to understand the nature of exchange interactions in spinel lattice, spin canting and cation distribution. Lithium ferrites doped with Zn 2~ have been studied [I, 2] and different interpretations were given for the decrease in magnetization at high Zn content. Young and Smit [I] concluded in their zero field, room temperature M6ssbauer study of the system Li~,~ ,5,Zn,Fe25 0~O4 that there is no significant spin canting in this system but merely reversal of the octahedral (B) spins with less than two tetrahedral (A) * Author to whom correspondence should be addres~d. Fe ~' nearest neighbours. Later, Rosenberg et al. [2] studied the same system at 4.2 K and in the presence of magnetic fields upto 70 kOe. They explained spin canting of the Fee'(B) spins to be the cause of the decrease in magnetization for Zn > 0.4. This is because of the presence of a large number of non-magnetic zinc ions at the A site which is qualita- tively explained by the Rosencwaig model [3]. This agrees with the neutron diffraction data of Zhilyakov et al. [4] and high field magnetization data of White et al. [5]. Dormann et al. [6-8] have investigated in detail the system with Ti 4~ and Zn-" substitutions, using different techniques like X-ray and neutron diffrac- tion, a.c. magnetic susceptibility, and M6ssbauer spectroscopy. In a study of the system Li05,0~,Ti, Fez5 ~5,O4he suggested the possibility of spin canting at the tetrahedral sites when t is large. In the present paper we substitute lithium ferrites with Ti 4÷ and Zn -'~ simultaneously, and report the investigations carried out using M6ssbauer spectro- scopy. The general formula of the system under study is Li0~5~05,Zn0~Ti, Fe2~5 15,O4 (0.0 <~ t ~< !.2). The quantity of Zn is kept fixed at 0.3 and the influence of varying Ti 4+ substitution on the various hyperfine interactions and cation distribution was investigated. Studies were made at 300 K and at 77 K. The effect of simultaneous substitution of equal amounts of Ti 4+ and Zn 2+ in the lithium ferrite system has been reported elsewhere [9]. 549