Emission Mössbauer study of CMR manganite La₀.₈Ca₀.₂MnO₃. I. Anomalous ferromagnetism

Abstract

Using ⁵⁷Co emission Mössbauer technique, we present clear evidence that in Ca-doped manganite, the magnetic and paramagnetic phases coexist below Tc, with the abundance of the latter increasing with temperature. In contrast with the regular ferromagnetic materials, the variation of the hyperfine internal magnetic field Hint with temperature deviates considerably from the Brillouin relation, and exhibits an abrupt drop at Tc. These features characterize the magnetic transition as a first-order transition. The non-Brillouin behavior of Hint(T) and the temperature dependence of the shape of the magnetically split sextet indicate the presence of spin fluctuations in this material well below Tc.