Magnetic aftereffect and electrical conductivity in double perovskite Ba2FeMoO6

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