Structural and Magnetic Behavior of Mn Doped Zno Synthesized By Soft Chemical Route

Abstract

Nanocrystalline undoped and 5% Mn doped ZnO powders are synthesized by sol-gel route using constituent nitrate and citrate precursors. The physico-chemical characterizations of powders calcined at various temperatures (400-1100 ˚C), are performed using techniques (XRD and SQUID) to study structural, nano/microstructural, and magnetic properties. XRD patterns clearly revealed the evolution of major wurtzite (ZnO) and minor non-stoichiometric defect cubic spinel phase of ZnMnO 3- . Unexpectedly, the magnetic hysteresis loop with its large magnetic parameters are observed at room temperature as soon as the concentration of the minor phase is large enough. The analysis of the unusual room temperature ferromagnetic behavior is presented in this communication based on the dominant contributions of the secondary nanocrystalline non-stoichiometric defect cubic spinel phase of ZnMnO 3- .KEYWORDS: Diluted magnetic semiconductor, soft chemical route, Mn doped ZnO, Room temperature ferromagnetism I. INTRODUCTION In the recent past, a surge of interest is observed in the studies of diluted magnetic semiconductor (DMS) oxides due to simultaneous utilization of charge and spin of electrons in a single material to develop new functionalities [1][2][3][4]. These DMSs are potential candidates for technological application such as spintronic devices. Recently, this class of materials is studied extensively for better understanding of basic mechanisms of different types of magnetic interactions in diluted system. Among these materials, we focused our attention on undoped and doped ZnO based DMS. Dietl et al reported room temperature ferromagnetic (RTFM) behavior arising from carrier mediated exchange interaction has been predicted for several transition metal (Mn, Fe, Co, etc) doped ZnO and GaN DMSs. [2]. The large amount of experimental work on Mn doped ZnO based DMSs has been reported in literature with contradictory experimental results in favor of RTFM [5][6][7] when processed at lower temperature and against of RTFM [8,9] when processed at higher temperature. Similar results are obtained in different product (bulk and nanoparticles) forms prepared by different synthesis along with different processing parameters [5][6][7][8][9]. In spite of the tremendous amount of experimental work, the origin of RTFM behavior and the associated energy exchange interactions are not fully understood. In the present investigation, the RTFM behavior of sol-gel synthesized nanoparticles of 5% Mn doped ZnO is discussed in terms of secondary nanocrystalline defect cubic spinel (DCS) phase of ZnMnO 3- .