Semiconducting single-layer(SL)and few-layer MoS2 have a flat surface,free of dangling bond.Using density functional theory coupled with non-equilibrium Greens function method,we investigate the spin-polarized transport properties of Co/2D MoS2/Co and Ni/2D MoS2/Ni junctions with MoS2 layer number of N = 1,3,and 5.Well-defined interfaces are formed between MoS2 and metal electrodes.The junctions with SL MoS2 spacer are almost metallic owing to the strong coupling between MoS2 and the ferromagnets,while those are tunneling with few layer MoS2 spacer.Both large magnetoresistance and tunneling magnetoresistance are found when fcc or hcp Co is used as electrodes.Therefore,flat single-and few-layer MoS2 can serve as an effective nonmagnetic spacer in a magnetoresistance or tunneling magnetoresistance device with a well-defined interface.