The effect of Ru doping on the alkali-doped manganite Pr0.8Na0.2MnO3

Polycrystalline manganites Pr0.8Na0.2MnO3 doped by ruthenium (0.0≤xRu≤0.2) were prepared by the sol–gel process. The magnetic field induced metamagnetism was observed to occur with a large resistivity drop at 3 K for xRu≤0.02 samples, which can be sorted into the kind of CMR phenomenon. It was found that the 0.01 Ru doping increased TC and decreased the metamagnetic critical field than that of the undoped sample. The doped manganites show a quick increase in their magnetic moments as xRu increases from 0.01 to 0.04, but the larger fraction of Ru doping (0.04≤xRu≤0.2) reduces their M and TC. All the five doped samples have larger magnetic moments than that of the host sample. Ru doping of xRu>0.01 results in a rapid disappearance for the observation of long range spin and charge ordering in the samples’ M–T curves, which is characteristic of the undoped sample. It was found that larger low-temperature MR favored decrease in the metamagnetic critical field. Finally, the phase diagram of Ru doping vs. transition temperatures is presented to summarize the experiments.