Tunnelling Magnetoresistance in NM/FI/NI/FI/NM Double Spin Filter Tunnel Junctions

On the basis of NM/FI/FI/NM double spin filter tunnel junction this paper proposes a new type of double spin filter tunnel junction,NM/FI/NI/FI/NM,by inserting a NI layer between two FIs in the old one,NM/FI/FI/NM.Here TMR,NM,FI and NI stand for the tunnelling magnetoresistance,nonmagnetic metal,ferromagnetic and nonmagnetic insulators(semiconductors),respectively.The effect of thickness of FI and NI on the TMR is studied theoretically in this work under a few biases,using the transfer matrix method in free electron approximation.The results show that in the new type of double spin filter tunnel junction a large TMR can still be achieved under suitable choice of the thickness.