Magnetic aftereffect and electrical conductivity in double perovskite Ba2FeMoO6

In this work a study of the magnetic aftereffect and electrical conductivity in Ba2FeMoO6 is presented. Aftereffect measurements have been performed by recording the time evolution of magnetic permeability just after the sample demagnetization, while the electrical conductivity has been obtained by means of the four-probe technique working under ac excitation. The isochronal relaxation spectrum was constructed by evaluating at each temperature the relative variation of permeability between the end of demagnetization and a set of indexed time windows according to the fastness of the magnetic relaxation. The magnetic aftereffect spectra show two well-defined peaks related to the magnetic phase transition and the orientational processes that can be fitted by activation energies close to 0.65 eV. Electrical conductivity presents metallic behavior in the ferromagnetic region and semiconducting response in the paramagnetic zone with activation energy of 0.03 eV. (C) 2001 American Institute of Physics.