Evolution of the Magnetic Ground State in the Electron-Doped Antiferromagnet CaMnO$_3$

Abstract

Measurements of the specific heat on the system Ca$_{1-x}$La$_{x}$MnO$_{3}$ (% $x\leq 0.10$) 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 $T_{N}$ from 122 K for the undoped sample to 103 K for $x=0.10$. The low temperature ($T<20$ K) heat capacity data is consistent with phase separation. The undoped sample displays a finite density of states and typical antiferromagnetic behavior. The addition of electrons in the $x\leq 0.03$ 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.