The specific heat of the perovskite manganite ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_{3+\delta }$ was measured in the doping regime $x=0.0\mathrm{}$ to 0.3 where at low temperatures the material changes from a layered antiferromagnetic insulator to a ferromagnetic metal. A term in the specific heat, $C\propto T^2$, is found in ${\mathrm{LaMnO}}_3$ that is attributable to spin excitations in a layered antiferromagnet. Ferromagnetic samples have the expected specific heat term $C\propto T^{3/2}$ due to ferromagnetic spin waves. The exchange coupling ( $J$), electronic linear term ( $\gamma$), Debye temperature ( ${\theta }_D$), and the local field at the Mn site ( $H_{\mathrm{hyp}}$) are extracted from the specific heat as functions of Sr doping.

• Received 8 November 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.3201