In the first and second parts of this dissertation structural stability, electronic structurernand magnetic interaction in transition metal(TM) atoms(V,Mn) doped monolayerrn(ML) and bilayer(BL)MoS2 are studied within the density function theory(DFT)rnbased on DFT+U formalism. It is found that,the injection of V andMn atoms inMornsite of ML and BL MoS2 introduces magnetism and turns semiconductor behaviorrnof host MoS2 to half metallic nature. The magnetic interaction between dopants inrnML and BL MoS2 are always ferromagnetic irrespective of dopant configurations.rnIn contrast, in V doped case the magnetic interaction oscillates from ferromagnetrnto antiferromagnet depending on the separation between dopants. Moreover,it isrnfound that interlayer interaction in doped BL MoS2 system affects not only electronicrnstructures but also the magnetic properties of the system. The calculatedrnferromagnetic transition temperature (TC) inMn doped ML and BLMoS2 cases arernfound to be above the room temperature (RT), whereas in V doped cases TC closerrnto RT. In addition, TC increases with doping concentrations in a range of dilute limitrn(6.5%) of magnetic atoms for doped ML and BL MoS2,which agrees with latest experimentalrnobserved RT TC .Therefore based on our result, we suggest thatMn andrnV doped ML and BL MoS2 are promising candidates for 2D DMS for high temperaturernspintronics applications. In third part of this dissertation,using low energyrneffective tight binding model together with consideration of dopant introduced exchangernfield it is found that spin orbit coupling together with exchange energy determinernthe valley polarization which in turn controls valley and spin Hall conductivityrnin doped ML MoS2 system. Our results form another important step towardsrninformation processing based on the valley degree of freedom.