Magnetization and resistivity steps in the phase separated Pr0.5Ca0.5Mn1-xNixO3 manganites

The low temperature magnetic and transport properties of the Pr0.5Ca0.5Mn1-xNixO3 manganites (0 less than or equal to x less than or equal to 0.1) have been investigated. The presence of Ni hinders the charge and orbital ordering observed in Pr0.5Ca0.5MnO3 and favors the creation of ferromagnetic regions, leading to phase separation. The ferromagnetic fractions induced by the Ni substitution have been estimated from magnetization measurements, they are large and reach 40% for 4% of Ni. Steps are observed in the M(H) and p(H) curves of all the samples at T < 5 K. They are similar to the steps observed in Pr(0.5)Ca(0.5)Mu(1-x)M(x)O(3), where M is a non magnetic cation (Mg2+, Ga3+,...), and for which the ferromagnetic fractions are very small (less than 2%), however, their appearance is restricted to lower temperatures (T < 5 K) with Ni dopant than with non magnetic cations. This study shows that steps can be observed in a wide range of phase-separated systems, even when the ferromagnetic fraction is very large.