Capacitive and magnetoresistive origin of magnetodielectric effects in Sm-substituted spiral antiferromagnet BiMnFe2O6

BiMnFe2O6 exhibits a spiral antiferromagnetic ordering below 212K and a reentrant spin glass transition at 34 K. Further, magnetic and dielectric anomalies occur at the same temperature (T = 170 K) with a significant magnetodielectric effect. Upon substitution of Sm3+ for Bi3+ ions in Bi1-xSmxMnFe2O6 (x = 0.1 and 0.2), the dielectric anomaly shifts to low temperatures (T = 135 and 72 K, respectively), whereas the magnetic anomaly develops into a weak ferromagnetism. For x = 0.2, the weak ferromagnetism occurs in a wide temperature range (90-201 K). Below 90 K, it undergoes a transition to an antiferromagnetic state. In contrast to the parent compound (x = 0), the magnetodielectric effect is observed both in the antiferromagnetic region (T < 90 K) with a maximum at the dielectric anomaly (72 K) and also in the weak ferromagnetic region. It has been shown that the magnetodielectric effect in the antiferromagnetic region has an intrinsic capacitive origin while that observed at the weak ferromagnetic region originates from magnetoresistance. (C) 2015 AIP Publishing LLC.