Anomalous Hall effect in beta-FeSi2

The dependence of the Hall resistivity pH on the magnetic induction B was i nvestigated on beta-FeSi2 single crystals and molecular-beam-epitaxy-grown layers. The strength of anomalous contributions to rho(H)(B) found in most samples critically depends on the growth conditions. Measurements of the ma gnetization ill were performed on single crystals. Measurements of rho(H)(B ) and M(B) were performed on the same sample, it is shown that the anomalou s contributions to rho(H)(B) have a magnetic origin. The measurements of M and the results of neutron diffraction gave no indication of a magnetic pha se transition of beta-FeSi2. It is suggested that the cause of the anomalou s contributions to the Hall resistivity found in most samples investigated is of extrinsic nature. We propose that the effects arise from clusterlike regions which carry large magnetic moments and behave superparamagnetically . [S0163-1829(98)06047-0].