Critical Exponents and Pressure Dependence of $T_c$ of La(Ca)MnO$_3$

Measurements of heat capacity and thermal expansion for La$_{1- x}$Ca$_{x}$MnO$_{3}$ with $x$ = 0, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, and 1 are reported. Using a model proposed previously (Souza et al. Phys. Rev. Lett. 94, 207209 (2005)), which utilizes both heat capacity ($C_{P}$) and thermal expansion coefficient ($\mu$) data, the pressure dependencies of $T_c$, d$T_{c}$/d$P$, are obtained for all samples. d$T_{c} $/d$P$ decreases as the Ca doping increases. Critical behavior using both $C_{P}$ and $\mu$ is evaluated for the samples. The critical exponent $\alpha$ increases from 0.13, for LaMnO$_{3} $ to 0.97 for $x$ = 0.30. As Ca content is increased further, $\alpha$ drops reaching 0.11, for CaMnO3.