Clear Experimental Signature of Charge - Orbital density wave in Nd 1 − x Ca 1 + x MnO 4

Single Crystals of Nd1−xCa1+xMnO4 have been prepared by the travelling floating-zone method, and possible evidence of a charge -orbital density wave in this material presented earlier [PRB68,092405 (2003)] using High Resolution Electron Microscopy [HRTEM] and Electron Diffraction [ED]. In the current note we present direct evidence of charge-orbital ordering in this material using heat capacity measurements. Our heat capacity measurements indicate a clear transition consistent with prior observation. We find two main transitions, one at temperature T H = 310− 314 K, and other at T A = 143 K. In addition, we may also conclude that there is a strong electron-phonon coupling in this material. PACS numbers: 78.20.-e, 78.30.-j, 74.76.Bz