Magnetic and magnetoelectric studies in pure and cation doped BiFeO3

We report the effect of divalent cation (A) substitution on magnetic and magnetoelectric properties in Bi(1-x)A(x)FeO(3) (A = Sr, Ba and Sr0.5Ba0.5; x = 0 and 0.3). The magnetization of undoped BiFeO3 shows a sharp peak at the Neel temperature T-N = 642 +/- 2 K and a subtle increase below 100 K. Both these features are masked in the co-doped sample (A = Sr0.5Ba0.5) which shows only a weak anomaly at T-N. All the divalent cation doped samples show enhanced magnetization with a well defined hysteresis loop compared to the parent compound. Both longitudinal (L-alpha(ME)) and transverse (T-alpha(ME)) magnetoelectric coefficients with dc magnetic field parallel with and perpendicular to the direction of induced voltage, respectively, were measured using dynamic lock-in technique. It is found that the T-alpha(ME) increases in magnitude and exceeds the L-alpha(ME) with increasing size of the A cation. The maximum T-alpha(ME) = 2.1 mV/cmOe in the series is found for A = Sr0.5Ba0.5, though it is not the compound with the highest saturation magnetization. The observed changes in the magnetoelectric coefficient are attributed to possible modification in the domain structure and magnetoelectric coupling in these compounds. (C) 2009 Elsevier Ltd. All rights reserved.