Ferromagnetism and thermoelectric power of La1.5Ca1.5Mn2O7

We report on the preparation, X-ray diffraction, ac susceptibility, dc magnetization and thermoelectric power (TEP) of La1.5Ca1.5Mn2O7. The compound has a tetragonal structure with lattice parameters a = 3.886(1) Å and c = 19.34(1) Å. Magnetic measurements reveal a ferromagnetic transition at around Tc = 215 K. TEP measurements indicate hole conductivity and has a maximum at Tc indicating an insulator to metal transition. Some possible reasons for the recently reported observation of Tc being far above the maximum of resistivity are pointed out.