Probing the existing magnetic phases in Pr_0.5Ca_0.5MnO₃ (PCMO) nanowires and nanoparticles: magnetization and magneto-transport investigations

Abstract

We show from conventional magnetization measurements that the charge order (CO) is completely suppressed in 10 nm Pr_0.5Ca_0.5MnO₃(PCMO 10) nanoparticles. Novel magnetization measurements, designed by a special high field measurement protocol, show that the dominant ground state magnetic phase is ferromagnetic-metallic (FM-M), which is an equilibrium phase, which coexists with the residual charge ordered anti-ferromagnetic phase (CO AFM) (an arrested phase) and exhibits the characteristic features of a 'magnetic glassy state' at low temperatures. It is observed that there is a drastic reduction in the field required to induce the AFM to FM transition (~5-6 T) compared to their bulk counterpart (~27 T); this phase transition is of first order in nature, broad, irreversible and the coexisting phases are tunable with the cooling field. Temperature-dependent magneto-transport data indicate the occurrence of a size-induced insulator-metal transition (T_{M - I}) and anomalous resistive hysteresis (R-H) loops, pointing out the presence of a mixture of the FM-M phase and AFM-I phase.