Magnetic and electronic phase transitions and magnetoresistance effect in the Pr 0.5−xLa xSr 0.5MnO 3 ( [formula omitted], 0.15) system

Abstract

The electronic and magnetic phase transitions of Pr 0.5− x La x Sr 0.5MnO 3 with x = 0.10 and 0.15 were investigated. The M( T) and ρ ( T ) curves for these samples clearly show transitions from antiferromagnetic insulator to ferromagnetic semiconductor, ferromagnetic metal and finally to paramagnetic semiconductor as the temperature is increased from 5 to 300 K. Especially, two obvious protrudent peaks in the magnetoresistance curves MR( T) for these samples were clearly observed in the relative low magnetic field, 1 T. One peak appears at around the antiferromagnet-ferromagnet transition temperature T N (∼150 K) with MR≈−23%, another occurs at around the ferromagnet-paramagnet transition temperature T C(∼275 K ) with MR≈−8.2%. In addition, when the magnetic field was increased, the temperature corresponding to the MR peak at T N shifts to lower temperature while the temperature corresponding to the MR peak at T C is fixed.