Structural and magnetic phase diagrams ofLa1−xSrxMnO3andPr1−ySryMnO3

Abstract

The nuclear and magnetic structures and properties of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$ with $0.45<~x<~1$ and ${\mathrm{Pr}}_{1\ensuremath{-}y}{\mathrm{Sr}}_{y}{\mathrm{MnO}}_{3}$ $(0.58<~y<~1)$ were investigated using neutron powder diffraction, resistivity and magnetic measurements. In this paper, we present the full magnetic and structural phase diagram for ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$ and a partial phase diagram for ${\mathrm{Pr}}_{1\ensuremath{-}y}{\mathrm{Sr}}_{y}{\mathrm{MnO}}_{3}.$ At low temperatures, we observe a series of structural phase transitions evolving as a function of increasing x as follows: orthorhombic $\mathrm{Pbn}\stackrel{\ensuremath{\rightarrow}}{m}\mathrm{rhombohedral}$ $R3\ifmmode\bar\else\textasciimacron\fi{}\stackrel{\ensuremath{\rightarrow}}{c}\mathrm{orthorhombic}$ $\mathrm{Fmm}\stackrel{\ensuremath{\rightarrow}}{m}\mathrm{tetragonal}$ $I4/mc\stackrel{\ensuremath{\rightarrow}}{m}\mathrm{cubic}$ $\mathrm{Pm}3\ifmmode\bar\else\textasciimacron\fi{}m.$ At higher temperatures, the orthorhombic Fmmm structural region disappears. We also identify four magnetic states (FM, A, C, and G type) evolving as a function of increasing x. The magnetic and nuclear structural transitions coincide for samples with $0.8<~x<~0.95.$ In the $0.5<~x<~0.9$ region, resistivity and magnetic measurements show a substantial hysteresis near ${T}_{N}.$ This hysteresis of a few K is indicative of a first order antiferromagnetic transition in good agreement with the neutron diffraction results. Our data also suggest the existence of a strong competition between the ferromagnetic and A-type states for $x\ensuremath{\sim}0.5,$ and between the C- and G-type states for $x\ensuremath{\sim}0.95.$ A similar behavior is observed for ${\mathrm{Pr}}_{1\ensuremath{-}y}{\mathrm{Sr}}_{y}{\mathrm{MnO}}_{3}.$