ELECTRON-SPIN-RESONANCE STUDIES IN BETA-FESI2 CRYSTALS - COMMENT

a recent article [J. Appl. Phys. 80, 1678 (1996)] Aksenov et al. repor ted on electron paramagnetic resonance (EPR) studies in beta-FeSi2 cry stals grown by chemical vapor transport, They did not perform a rigoro us measurement of the angular variation of the EPR line positions. Con sequently, there has been a drastic loss of information and most of th eir conclusions turn out to be erroneous, It is shown that the anisotr opic signals (A(i),B-i) do not arise from spin tripler states but from centers with S=1/2 and their origins are not Ni2+ ions but Ni+ (A(i)) and Cr- (B-i) ions substituting for Fe on one of its two inequivalent lattice sites. The analysis of the line structure of the isotropic si gnal (C) is incorrect and hence, the structure cannot be attributed to a ligand hyperfine interaction with four iron atoms. Finally, the det ermination of an acceptor activation energy from the temperature depen dence of the C signal is not justified since no correction for the EPR intensity dependence due to the thermal population difference of the Zeeman levels was included. (C) 1997 American Institute of Physics.