Hall effect and resistivity of β-FeSi2 thin films and single crystals

Cr-doped and undoped beta-FeSi2 thin films were deposited on (001) and (111) Si substrates by molecular beam epitaxy. Single crystals were grown by the chemical vapor transport technique. In thin films we found a significant substrate influence on the Hall voltage at room temperature which was strongly reduced at lower temperatures. In Cr-doped samples a transition between defect-band conduction and valence-band conduction was observed in the temperature range 50-100 K. The behavior of the mobility curves mu(T) suggests that defect-band conduction dominates up to near room temperature in nominally undoped thin films. Below a sample-dependent temperature, being not higher than 150 K, often a nonlinear dependence of the Hall effect on the magnetic field was found, sometimes accompanied by pronounced hysteresis behavior. It is shown that this behavior is rather related to microinhomogeneities than to a magnetic phase transition. (C) 1998 American Institute of Physics.