Anisotropic hyperfine field fluctuation in Sr{sub 2}FeMoO{sub 6}

The double perovskite Sr{sub 2}FeMoO{sub 6} has been studied by the Mossbauer technique, neutron, and x-ray diffraction. The structure is found to be tetragonal with lattice constants a{sub 0}=5.5729Aa and c{sub 0}=7.9077Aa. Mossbauer spectra and neutron diffraction measurements of Sr{sub 2}FeMoO{sub 6} have been taken at various temperatures ranging from 10 to 473 K. The low-field magnetoresistance magnitude ({Delta}{rho}/{rho}{sub 0}) at 500 Oe was 3.1% and 1.8% at 77 and 300 K, respectively. As the temperature increases toward to the Curie temperature, T{sub C}=425K. Mossbauer spectra show the line broadening and 1, 6 and 3, 4 linewidth difference because of anisotropic hyperfine field fluctuation. The anisotropic field fluctuation of +H(P{sub +}=0.85) was great than {minus}H(P{sub {minus}}=0.15). We also calculated frequency factor and anisotropy energy with values of 9.8 {Gamma}/{Dirac_h} and 149.6 erg/cm3, respectively, using the relatively accurate data for T=260K which is associated with the large line broadening. {copyright} 2001 American Institute of Physics.