Anomalous anisotropic ac susceptibility response ofLa1−xSrxMnO3(x≈1/8)crystals: Relevance to phase separation

Abstract

The dynamic response of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$ crystals $(x=0.1$ and 0.125) has been studied by ac susceptibility. A strongly frequency- and field-dependent susceptibility anomaly was observed along a and b axes in the intermediate temperature range between the onset of magnetic order and the orthorhombic--``pseudocubic,'' ${\mathrm{O}}^{\ensuremath{'}}\ensuremath{-}{\mathrm{O}}^{\ensuremath{''}},$ structural transition. No anomaly was present if the ac field was applied along the c axis. This unusual response, reminiscent of cluster-glass behavior, is attributed to a strongly anisotropic, magnetically nonuniform state. This observation would constitute a clear indication of phase separation in low-doped manganites.