Structural, electrical, and magnetic transport properties of La0.72Ca0.28Mn1_xCrxO3 (0=??????? x =0.06) ceramics

To obtain comprehensive materials with both high temperature coefficient of resistivity (TCR) and magnetoresistance (MR) at low magnetic fields, polycrystalline La0.72Ca0.28Mn1_xCrxO3 (x = 0, 0.02, 0.04, 0.06) ceramics were prepared herein by sol-gel method. Electronic configuration of Cr3+ ions is similar to that of Mn4+ ions, therefore, successive substitution of Mn with Cr increases electrical resistivity and decreases metal-insulator transition temperature of ceramics, even yielding hump-like feature for Cr-rich (x = 0.06) samples. The best TCR (28.50%.K_1) and MR (72.37%) values were obtained simultaneously at Cr dopant content of 0.02 (La0.72Ca0.28Mn1_xCrxO3). Strong response of the material to temperature and magnetic field was caused by minimal symmetry of orthorhombic structure and the most robust Jahn-Teller distortion. With increasing Cr content, Mn3+/Mn4+ or Mn3+/Cr3+ double exchange was diluted, and Cr3+/Cr3+ or Cr3+/Mn4+ superexchange was promoted. However, the internal competition effect was not conducive to the improvement of material properties.