Magnetic and electron paramagnetic resonance studies of Ln0.5Ca0.5MnO3 (Ln = Pr, Bi) manganite

In this paper we compare the magnetic and electron paramagnetic resonance (EPR) properties of Pr0.5Ca0.5MnO3 (PCMO) and Bi0.5Ca0.5MnO3 (BCMO) charge ordered manganites. PCMO and BCMO samples were prepared by solid state reaction method. A commercial SQUID magnetometer was used to study the dc-magnetization in the temperature range of 10-300 K. The EPR experiments were carried out using a commercial X-band (frequency ∼ 9.4 GHz) spectrometer in the temperature range 4 K – 300 K. Marked differences are found when the magnetic and EPR properties of rare earth (PCMO) and bismuth based manganites (BCMO) are compared. The temperature dependent resonance fields of PCMO and BCMO samples are seen to be opposite to each other. PCMO shows the resonance field behavior similar to other charge ordered manganites, i.e., decreases with the decrease in temperature whereas the resonance field of BCMO increases with a decrease in temperature. The opposite behavior of resonance field could be due to the different magnetic structures present in the BCMO manganite.