Clinching experimental evidence of "Room Temperature Ferromagnetic Behavior" in 5 mol% Mn doped SrTiO3

Abstract

Theoretical prediction and rare experimental observation of room temperature ferromagnetism in transition metal doped semiconductors/insulators such as ZnO, TiO2, SrTiO3 and BaTiO3 has been of key fundamental interest in understanding materials [1-3]. In this work, 5 mol% of Mn doped SrTiO3 was synthesized by chemical coprecipitation [4]. This synthesis technique has been adopted specifically to ensure the most homogeneous doping of Mn in SrTiO3 lattice thus largely preventing the formation of any other impurity phases. Analysis of high resolution XRD data collected for the sample sintered at 1150°C revealed that the phase was of high purity. Magnetization measurements were carried out on the same sample where the variation of Magnetization (M) with temperature under both zero field cooled (ZFC) and field cooled conditions (FC) were measured under an applied magnetic field (H) of 100 Oe. The trend in ZFC is quite contrary to the expected paramagnetic nature in this system. The increase in ZFC magnetization values when the temperature was increased beyond 150 K has to be taken into consideration [Fig. 1]. Also the dispersion in the ZFC and FC curves is quite significant near room temperature and there is a difference of an order in the ZFC and the FC magnetization values around 300 K unlike conventional paramagnetic systems. Therefore the temperature dependent magnetization data (>150 K) clearly exhibits the sign for an impending ferromagnetic behavior around RT. The M versus H behavior was studied in the -1.5 T to 1.5 T range at three different temperatures - 10 K, 150 K and 300 K. Saturated hysteresis loop observed at RT corroborates our observation of the bifurcation observed in ZFC/FC behavior around 300 K [Fig.2]. At 10 K, hysteresis loop turns to look more paramagnetic-like indicating the presence of only a weak ferromagnetic ordering with a strong paramagnetic matrix. A suitable mechanism based on defects induced by Mn doping in SrTiO3 will be discussed to explain this observation of RT Ferromagnetic behavior [5].