Controllable valley and spin-polarized transport and negative magnetoresistance in a silicene junction

We investigate the valley and spin-resolved transport through a ferromagnetic/ferromagnetic/ferromagnetic silicene junction. For the normal silicene junction with zero exchange field in the presence of photo-irradiation, we observe a 100% valley/spin polarization by modulating the energy E. By enhancing the strength of the photo-irradiation or the gate voltage in the middle layer VM, a 100% spin and large valley polarization can be found. If the staggered exchange field is considered instead of the photo-irradiation, by tuning E a fully polarized valley/spin transport is demonstrated. By tuning the staggered exchange field or VM, a 100% valley and large spin polarization can be seen. In the ferromagnetic/normal/ferromagnetic junction, depending on the polarized direction of the circularly polarized light, a large negative or positive magnetoresistance can be obtained. The results obtained here can be explained by the band structures of the device.