Magnetoresistance in Parent Pnictide AFe₂As₂(A=Sr, Ba)

Magnetoresistances of SrFe₂As₂ and BaFe₂As₂ in the magnetic ordered state are studied. Positive magnetoresistance is observed in the magnetic fields H applied in the azimuthes of θta = 0°and 30° with respect to the c-axis. The magnetoresistance can reach 20% for SrFe₂As₂ and 12% for BaFe₂As₂ at H = 9 T with θ= 0°(H || c). Above the magnetic transition temperature, the magnetoresistance becomes negligible. The data in the magnetic ordered state could be described by a modified two-band galvanomagnetic model including the enhancement effect of the applied magnetic field on the spin-density-wave gap. The field enhanced spin-density-wave gaps for different types of carriers are different. Temperature dependencies of the fitting parameters are discussed.