Multiferroic tunnel junction of Ni50.3Mn36.9Sb12.8/BiFeO3/Ni50.3Mn36.9Sb12.8 for magneto-electric random access memory devices

A multiferroic tunnel junction composed of two ferromagnetic shape memory alloy electrodes separated by a multiferroic barrier was fabricated from a Ni50.3Mn36.9Sb12.8/BiFeO3/Ni50.3Mn36.9Sb12.8 trilayer. A large exchange bias field (H-EB) of similar to 59 Oe at room temperature was found for this trilayer. Besides the exchange bias effect in this multiferroic tunnel junction, one of the most interesting results was the magnetoelectric effect, which is manifested by the transfer of strain from the Ni50.3Mn36.9Sb12.8 electrodes to the BiFeO3 tunnel barrier. The magnetic field dependence of the junction resistance was observed at room temperature after aligning the ferroelectric polarization of the BiFeO3 barrier with the poling voltage of +/- 3V. A change in junction resistance was also observed between the magnetic parallel and antiparallel states of the electrodes, suggesting an entire flip of the magnetic domains against the magnetic field. After reversing the polarization of the BiFeO3 barrier between the two directions, the entire R-H curve was shifted so that both parallel and antiparallel resistances switched to different values. Hence, after applying positive and negative voltages, two parallel and two antiparallel states, i.e., four distinct states were observed. These four states will encode quaternary information by both ferromagnetic and ferroelectric order-parameters, to read non-destructively by resistance measurement. These findings may be helpful towards reconfigurable logic spintronics architectures in next generation magneto-electric random access memory devices. (C) 2016 AIP Publishing LLC.