2D materials are widely investigated for application in nanodevices and spintronics. Here, we demonstrate that a family of structures, LaOMS (M = Ti, V, and Cr), where a LaO layer is sandwiched between two magnetic MS layers, are suitable to be used as spin valves without contact. We show that they are stable and exhibit unique magnetic and electronic properties. We find that (1) each MS layer is ferromagnetic with the magnetic moment mainly contributed by the M ion and the coupling between the two MS layers in one structure is negligible due to the blocking of the LaO layer; (2) LaOMS can be a half-metal in the ferromagnetic (FM) state and a conductor in the interlayer antiferromagnetic (inter-AFM) state, and the total energies of the two states are almost identical; (3) the magnetic properties and exchange energy can be effectively controlled by contacting with other materials; and (4) a 100% spin current is achieved in FM LaOMS. Our results provide not only novel structures for practical application in spintronics, but also strategies for designing new devices.