Thermal activation and ac-field-induced discontinuous domain jumps in perovskiteLa0.7Ca0.3MnO3

Abstract

Low-field ac susceptibility was measured on bulk ${\mathrm{La}}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_{3}$ prepared by a partial melting technique. Discontinuous jumps with heights of $(1--2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\mathrm{emu}$ at temperature intervals of 3--5 K were observed in the ac susceptibility. 28 jumps were observed in the temperature range between 4.2 K and the Curie temperature of 250 K, with an ac field amplitude of 1 Oe, a frequency of 117 Hz, and a dc bias field of 5 and 20 Oe. Upon increasing the frequency up to 5000 Hz, the jumps shifted to lower temperature. For a dc bias field of 50 Oe and an ac field with an amplitude of 0.1 Oe and a frequency between 117 and 5000 Hz, only three jumps with heights of about $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\mathrm{emu}$ at large temperature intervals of about 60 K were observed for $T<{T}_{c}.$ With increasing frequencies, the three jumps shifted to lower temperatures without changing jump height. The discontinuous jumps in ${\mathrm{La}}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_{3}$ were interpreted in terms of thermally and ac-field-activated domain-wall jumps.