Low-Temperature Specific Heat of La1-xSrxMnO3+δ

The specific heat of the perovskite manganite La_1-xSr_xMnO_3+δ was measured in the doping regime x = 0.0 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~T², is found in LaMnO₃ that is attributable to spin excitations in a layered antiferromagnet. Ferromagnetic samples have the expected specific heat term C~T^3/2 due to ferromagnetic spin waves. The exchange coupling ( J), electronic linear term ( γ), Debye temperature ( θ_D), and the local field at the Mn site ( H_hyp) are extracted from the specific heat as functions of Sr doping.