Metallicity and associated ferromagnetism in fluorine doped LaMnAsO

The electrical and magnetic properties of the layered oxypnictide LaMnAsO have been investigated through fluorine doping at the oxygen site. LaMnAsO is well-established as an insulator and exhibits antiferromagnetic behavior below its Neel temperature, T _N = 360 K. With F-doping, the electrical and magnetic characteristics undergo a transition from insulating antiferromagnetic states to semiconducting and then to metallic ferromagnetic states. With F-doping levels ranging from approximately x = 0 . 15 to nearly its maximum at 0.25, the resistivity experiences a remarkable reduction by five orders of magnitude, reaching values of approximately 0.04 Ω cm at room temperature. Furthermore, the temperature-dependent resistivity profile demonstrates a decidedly metallic nature for the F-doping ranges of x = 0 . 15 to 0.25. The transition temperatures (T _C ) exhibit a spread of approximately 20 K around 300 K. Notably, the transverse magnetoresistance (MR) is approximately 12% in the vicinity of the room temperature transition.