Structure and properties of La–Ca–Mn–O composites prepared by the glass-ceramic method

Abstract

A composite mixture of the colossal magnetoresistive oxide, La 0.67Ca 0.33MnO 3 and non-magnetic, insulating silicate/borate has been prepared, using the glass route with different nucleating agents. It is found that Sb 2O 3 is very effective in preferentially nucleating the LCMO phase compared to Cr 2O 3. The LCMO phase present in the as-quenched state in the three cases is found to grow as a result of annealing at 900 °C only when nucleated with Sb 2O 3. In the other two cases, simultaneous growth of other crystalline phases, such as LaBO 3 and CaB 2O 4 is found to be accompanied with the growth of LCMO. The magnetic studies show that the LCMO phase nucleated by Sb 2O 3 has the highest value of magnetization. The magnetization, however, was found to be lower than the bulk value, indicative of the presence of magnetic disorder and non-magnetic phases, which was observed in the electrical transport behavior also. The LCMO phase nucleated with either of the nucleants, Sb 2O 3 or Cr 2O 3, has a high resistivity compared to the LCMO phase formed without any nucleants.