Tunneling magnetoresistance of the double spin-filter junctions at nonzero bias

A recent theoretical estimation indicated that the NM/FI/FI/NM double spin-filter junction(DSFJ,here the NM and FI represent the nonmagnetic electrode and the ferromagnetic insulator(semiconductor)spacer,respectively)could have very high tunneling magnetoresistance(TMR)atzero bias.To meet the requirement in research and application of the magnetoresistance devices,we have calculated the dependences of tunneling magnetoresistance of DSFJ on the bias(volt-age),the thicknesses of ferromagnetic insulators(semiconductors)and the average barrier height.Our results show that except its very high value,the TMR of DSFJ does not decrease monoto-nously and rapidly with rising bias,but increase slowly at first and decrease then after havingreached a maximum value.This feature is in distinct contrast to the ordinary magnetic tunnel junc-tion FM/NI/FM(FM and NI denote the ferromagnetic electrode and the nonmagnetic insulator(semiconductor)spacer,respectively),and is of benefit to the use of DSFJ as a magnetoresistancedevice.