Inverse TMR in a nominally symmetric CoFe/AlOx/CoFe junction induced by interfacial Fe3O4 investigated by STEM-EELS

► Inverse TMR in the Ag buffered MTJ is due to Fe3O4 formed at CoFe/AlOx interfaces. ► STEM EELS SIs provide the evidences for formation of Fe3O4. ► High oxygen solubility in Ag can be the reason for the formation of Fe3O4.