Magnetic, electron magnetic resonance and optical studies of Pr_0.7Pb_0.3MnO₃ nanoparticles

Abstract

In this paper we present the preparation and physical property studies on Pr_0.7Pb_0.3MnO₃ (PPMO) nanoparticles with an average grain size of 5 nm. We find from SQUID magnetometry measurements that the Curie temperature (_TC) remains unaltered at 205 K with decrease in the particle size down to 5 nm in comparison with bulk T_C (200 K). From electron magnetic resonance (EMR) measurements, it is found that PPMO nanoparticles are more homogeneous than bulk PPMO. Only one EMR signal is observed down to 4 K in PPMO with an average particle size of 5 nm in contrast to the two EMR signal behaviour observed in bulk PPMO (200-240 K). The origin of the two EMR signals in the bulk was attributed to possible phase separation (Padmanabhan B et al 2007 Physica B 398 107). Such a phase separation is therefore concluded to be absent in nano-PPMO. In addition, temperature-dependent optical phonon measurements performed on 5 nm PPMO nanoparticles indicate the insulator-metal transition TMI = 230 K, which is nearly the same as that of the bulk sample (T_MI = 235 K).