Magnetic phase transitions and magnetoresistance in the La0.7Ba0.3(Mn1−xMex)O3 (Me=Fe, Al) single crystals and La0.7Sr0.3(Mn1−xMex)O3 (Me=Fe, Cr, Al) ceramics

Abstract The single crystals of La 0.7 Ba 0.3 (Mn 1− x Fe x )O 3 ( x ⩽0.28) and La 0.7 Ba 0.3 (Mn 1− x Al x )O 3 ( x ⩽0.15) compositions were grown using flux method and characterized by X-ray, electrical and magnetization measurements. The Fe-doping above x =0.2 destroys a long range ferromagnetic order thus leading to a spin glass state. It is found that insulating spin glasses exhibit a large magnetoresistance in the paramagnetic region which is comparable to that for ferromagnetic crystals showing metal–insulator transition close to T C . The magnetic behavior of La 0.7 Ba 0.3 (Mn 1− x Me x )O 3 (Me=Fe, Cr, Al) ceramics is in agreement with superexchange magnetic interactions via oxygen.