Canted antiferromagnetism in an insulating lightly doped La1-xSrxMnO3 with x

Abstract

We have investigated the magnetic structure of an insulating lightly doped ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{MnO}}_{3}$ with x=0.04,0.125, and 0.17 with neutron scattering technique and bulk magnetization measurements. The magnetic structure of the x=0.04 sample at 5 K is a commensurate layer-type (A-type) antiferromagnetism with the propagation vector [010] and the moment of 3.7\ifmmode\pm\else\textpm\fi{}0.2${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$/Mn, being parallel to the [100] axis in the orthorhombic Pnma symmetry. In addition, a spontaneous magnetization of 0.28\ifmmode\pm\else\textpm\fi{}0.02${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$/Mn is observed at 8 K by magnetization measurement. By contrast, the x=0.125 sample exhibits a large ferromagnetic moment of 3.7\ifmmode\pm\else\textpm\fi{}0.2${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$/Mn and a small A-type antiferromagnetic component of 0.23\ifmmode\pm\else\textpm\fi{}0.1${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$/Mn, while the x=0.17 sample exhibits only a ferromagnetic component of 3.6\ifmmode\pm\else\textpm\fi{}0.2${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$/Mn. These results are consistent with a spin structure derived from the conventional double exchange mechanism, but rule out the possibility of a recently suggested spiral spin structure for the insulating ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{MnO}}_{3}$ system. \textcopyright{} 1996 The American Physical Society.