Evolution of the magnetic ground state in the electron-doped antiferromagnet CaMnO3 -: art. no. 014403

Measurements of the specific heat on the system CaxMnO3 (xless than or equal to0.10) are reported. Particular attention is paid to the effect that doping the parent compound with electrons by substitution of La for Ca has on the magnetic ground state. The high- (T>40 K) temperature data reveal that doping decreases T-N from 122 K for the undoped sample to 103 K for x=0.10. The low temperature (T<20 K) heat-capacity data are consistent with phase separation. The undoped sample displays a finite density of states and typical antiferromagnetic behavior. The addition of electrons in the xless than or equal to0.03 samples creates local ferromagnetism as evidenced by a decreased internal field and the need to add a ferromagnetic component to the heat-capacity data for x=0.03. Further substitution enhances the ferromagnetism as evidenced by the formation of a long-range ferromagnetic component to the undoped antiferromagnetic structure. The results are consistent with a scenario involving the formation of isolated ferromagnetic droplets for small x that start to overlap for xapproximate to0.06 giving rise to long range ferromagnetism coexisting with antiferromagnetism.