The effect of Ni doping on the magnetic and transport properties in Pr0.5Ca0.5Mn1−xNixO3 manganites

Abstract

Structural, magnetic, and transport properties in Pr0.5Ca0.5Mn1−xNixO3 (x=0, 0.04, 0.07, 0.1) were investigated. It is remarkable that low Ni-doping levels at Mn sites induce drastic changes in the physical properties of Pr0.5Ca0.5MnO3 due to melting of the charge ordered state and the consequent capability of Ni ions to create ferromagnetic (FM) clusters. It was found that oxygen deficient samples (3−δ=2.84±0.03) exhibit resistivities higher by four to five orders than that of their stoichiometric counterparts and do not exhibit metal-insulator transition. Only a stoichiometric x=0.04 sample with higher content of the FM phase shows metal-insulator transition at T≈80 K. A change in slope in the zero field cooling magnetization curve observed for x=0.04 and 0.07 (may be slightly oxygen deficient samples) are indicative of spin-glass-like state. Applied hydrostatic pressure of about 10 kbars reduces the temperature of charge ordering in x=0 sample by about 10 K indicating on pressure induced suppression of the Jahn–Teller distortions. In distinct contrast to the behavior of Pr0.5Ca0.5Mn1−xCrxO3 samples, an applied pressure only slightly affects magnetization of x=0.04 and 0.07 samples possibly due to the difference in magnetic states obtained by substitution of Cr3+ and Ni2+. Electron magnetic resonance (EMR) unambiguously evidences on appearance of a FM phase on Ni doping. Temperature dependence of EMR spectra allow distinguishing between the magnetic states of two 4% Ni-doped samples and to speculate on the effect of magnetic inhomogeneities on the formation of the observed magnetic properties.