Inducement of ferromagnetic-metallic phase in intermediate-doped charge-ordered Pr 0.75 Na 0.25 MnO 3 manganite by K + substitution

Polycrystalline Pr 0.75 Na 0.25- x K x MnO 3 ( x = 0, 0.05, 0.10, 0.15 and 0.20) ceramics were prepared using conventional solid-state method and their structural, magnetic and electrical transport properties were investigated. Magnetization versus temperature measurements showed un-substituted sample exhibited paramagnetic behavior with charge-ordered temperature, T CO around 218 K followed by antiferromagnetic behavior at transition temperature, T N ∼ 170 K. K + -substitution initially weakened CO state for x = 0.05–0.10 then successfully suppressed the CO state for x = 0.15–0.20 and inducing ferromagnetic-paramagnetic transition with Curie temperature, T C increased with x . In addition, deviation of the temperature dependence of inverse magnetic susceptibility curves from the Curie-Weiss law suggests the existence of Griffiths phase-like increased with x . Magnetization versus magnetic field curves show existence of hysteresis loops at T x = 0) and T x = 0.05–0.10), which related to metamagnetic transition occurring at critical field. Electrical resistivity measurements showed an insulating behavior for x = 0 sample while for x = 0.05–0.20 samples showed metal-insulator transition and transition temperature, T MI increased with x . The increased in T C and T MI are attributed to the increase in tolerance factor which indicates reduction in MnO 6 octahedral distortion consequently enhanced double exchange interaction.