Evolution of the Magnetic Ground State in the Electron-Doped Antiferromagnet CaMnO₃

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Measurements of the specific heat on the system Ca₁₋ₓLaₓMnO₃ (% x≤ 0.10) 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 reveals that doping decreases Tₙ from 122 K for the undoped sample to 103 K for x=0.10. The low temperature (T<20 K) heat capacity data is consistent with phase separation. The undoped sample displays a finite density of states and typical antiferromagnetic behavior. The addition of electrons in the x≤ 0.03 samples creates local ferromagnetism as evidenced by a decreased intermanl 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 spin density wave.