Influence of Cr-doping on the magnetic and electrical transport properties of Nd0.75Na0.25MnO3

Polycrystalline Ndo. 75Na0.25Mn1-xCrxO3 (0≤x≤.1) samples were prepared by sol-gel method and their magnetic and electrical transport properties were investigated experimentally. The parent compound with x=0 was a charge ordered manganite and the charge ordering transition occurred at 170 K. For lower Cr concentration (x＜0.03), the samples preserved the charge ordering features of the parent compound,but the charge ordering transition temperature decreased with increasing x, in particular from 170 K for x=0 to 154 K for x=0.02. For the x≥0.03 samples, paramagnetic to ferromagnetic phase transition took place and the Curie temperature increased from 112.8 K for x=0.04 to 125.5 K for x=0.1. The electrical transport properties were also influenced by Cr doping. For x＜0.03, the samples displayed insulator characteristics below 300 K. For x=0.04, the sample showed insulator-metal transition around 75 K. For x＞.05, the insulator-metal transition disappeared and the compounds showed insulator features again. The magnetic and electrical properties could be well explained by the phase separation scenario.