Preparation and study of structural, electrical and magnetic properties of La_2SrFe_2O_7 and La_2SrMn_O_7

摘要

Ruddlesden-Popper type phases La_2SrFe_2O_7 and La_2SrMn_O_7 have been prepared by traditional ceramic method and their crystal structure has been determined by powder X-ray diffraction study. The iron compound has a tetragonal unit cell with a = 3.916 A and c = 20.463 A, while the phase containing manganese has a = 3.868 A and c = 20.205 A in the space group I4/mmm. La_2SrMn_2O_7 is ferromagnetic in the temperature 77-300 K and exhibits spin state transition above 210 K, while La_2SrFe_2O_7 is antiferromagnetic. Both the phases are insulators and electrical conduction in La_2SrMn_O_7 is a function of transition in magnetic behaviour of the metal ion M n~(3+), while insulator behaviour is more pronounced in La_2SrFe_2O_7.