Magneto-transport and optical properties of La0.7K0.3Mn(1−x)GaxO3 (0 ≤ x ≤ 0.25) ceramics

The effect of gallium doping on the structural, optical, and magneto-transport properties of the La0.7K0.3Mn(1−x)GaxO3 (0 ≤ x ≤ 0.25) ceramics in several magnetic fields (0T–3T) have been synthesized by Pechini sol–gel method. The Rietveld refinements data revealed that all the samples have a rhombohedral structure with the space group R3 ̅c. The SEM images recorded at different magnification levels reveal uniform grain shapes with flat surfaces. The optical properties indicated that the band gap of La0.7K0.3Mn(1−x)GaxO3 (0 ≤ x ≤ 0.25) ceramics was shifted from 3.2 to 3.08 eV with dopant concentration. The magnetic study confirmed that our compounds exhibit a ferromagnetic–paramagnetic transition in the vicinity of the Curie temperature Tc. Moreover, in the electrical part, the resistivity decreased with the Ga content and the metal–insulator transition temperature (TM-I) reached room temperature for x = 0.125 under a magnetic field of 3T. On the other hand, the magnetoresistance (MR) and temperature coefficient of resistance (TCR) increased with the doping of Ga until a significant maximum (MR = 88%, TCR = 8% K−1) around metal–insulator transition TM-I = 300 K for x = 0.125 with a magnetic field of 3T.