Electric, magnetic, and calorimetric properties and phase diagram ofPr1−xCaxCoO3(0<~x<~0.55)

Abstract

Resistivity, dc magnetization, ac susceptibility, and heat-capacity measurements were carried out for polycrystalline ${\mathrm{Pr}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{CoO}}_{3}$ $(0l~xl~0.55).$ Insulating, metallic, and metal-insulator transition (MIT) regions appear successively with increasing x. The boundary compositions of neighboring regions are between $x=0.1$ and 0.2 and between $x=0.45$ and 0.5. In the insulating region, the sample is an insulator and shows no phase transition in the range of 2--300 K. In the metallic region, the sample is a metal and shows a ferromagnetic ordering below about 80 K. In the MIT region, the sample shows a metal-insulator transition above about 80 K and a ferromagnetic ordering at around 5 K. The electronic and spin states of each phase are discussed based on the experimental results.