SPIN GLASS-TYPE BEHAVIOR IN IRON ANTIMONATE - THE IDENTIFICATION OF UNUSUAL PHENOMENA AT LOW-TEMPERATURES IN LOW MAGNETIC-FIELDS

We recently showed that iron antimonate of composition FeSbO4 undergoes a spin glass transition at ca. 20 K. New magnetic susceptibility measurements which we have subsequently recorded in low magnetic fields of 50 and 100 Oe show that the magnetic behavior at temperatures below ca. 80 K is more complex than was initially observed. Two peaks in the zero field cooled magnetic susceptibility data have been determined at temperatures of ca. 70 and 25 K. Neutron powder diffraction patterns recorded at temperatures below 160 K show a peak of magnetic origin which can be indexed as (100). The absence of a magnetic contribution associated with the (001) peak is indicative of a highly anisotropic spin structure. Analysis of the linewidth of the (100) reflection indicates a finite antiferromagnetic spin correlation within the (001) plane which increases in length to a maximum of ca. 30 Å with decreasing temperature until ca. 70 K when saturation occurs. The low field magnetic susceptibility data and the neutron diffraction results may be associated with an inhibited antiferromagnetic transition. The processes may be associated with the formation at ca. 70 K of clusters of ca. 30 Å of imperfectly antiferromagnetically ordered Fe3+ ions and the subsequent onset at ca. 25 K of magnetic interactions between the clusters. © 1990.