Ferromagnetism in fluorine doped LaMnAsO*

The electrical and magnetic properties of F-doped LaMnAsO have been investigated using x-ray diffraction, magnetization, electrical resisitivity and magnetoresistance measurements. LaMnAsO is wellestablished 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 change from an insulating antiferromagnetic state to a metallic ferromagnetic state. With F-doping levels in the range x ∼ 0.15 to 0.25, the resistivity shows a strong reduction by five orders of magnitude, reaching values of approximately ∼0.05 Ω·cm. Furthermore, the temperature-dependent resistivity profile demonstrates a decidedly metallic behavior in this range of composition. The transition temperatures (Tc) exhibit a spread of approximately 20K around 300K. Notably, the transverse magnetoresistance is approximately 12% at 300 K.