Increase of magnetic and magnetoelectric properties in Co/Mn co-doped BiFeO3 multiferroic

Co and Mn co-doped BiFeO3 samples are successfully realized using a stirred hydrothermal route to form BiFe0.9CoxMn0.1-xO3 (for x = 0.01, 0.03, 0.05, 0.07 and 0.09) system. Our data show that both the ferroelectric (T-C) and antiferromagnetic (T-N) transition temperatures increase especially T-N varies by up to 23 degrees C when changing from BiFe0.9Co0.01Mn0.09O3 to BiFe0.9Co0.09Mn0.01O3. Such strong T-N enhancement is explained by Co ionic size which induces a chemical pressure by reducing the unit cell and consequently favor the exchange coupling between the magnetic moments carried by Fe/Co/Mn. Moreover, Co3+ (d(6) electronic configuration) by replacing Fe (d(5)) increases the magnetization reaching a value of 3.394 emu/g for BiFe0.9Co0.09Mn0.01O3, by favoring double exchange interactions. The direct magnetoelectric (ME) measurements on those samples show a significant increase of the ME coefficient with a value of 8.720 mV/(Oe.cm) for BiFe0.9Co0.05Mn0.05O3 i.e. up to 6 times higher than that of pure BiFeO3. For Mn-rich compositions, because of a parasitic Bi25FeO40 phase and high electric losses, no intrinsic ME coefficient could be measured.