Heat conduction and magnetic phase behavior in electron-doped Ca_1-xLa_xMnO₃ (0≤x≤0.2)

Measurements of thermal conductivity (K) vs temperature are reported for a series of Ca_1-xLa_xMnO₃(0≤x≤0.2) specimens. For the undoped (x = 0), G-type antiferromagnetic compound a large enhancement of κ below the Neél temperature (T_N∼125 K) indicates a strong coupling of heat-carrying phonons to the spin system. This enhancement exhibits a nonmonotonic behavior with increasing x and correlates remarkably well with the small ferromagnetic component of the magnetization reported previously [Neumeier and Cohn, Phys. Rev. B 61 14319 (2000)]. Magnetoelastic polaron formation appears to underly the behavior of K and the magnetization at x⊖0.02.