Si-29 nuclear magnetic resonance spectra and relaxation in epsilon-FeSi

The magnetic properties of epsilon-FeSi are studied by Si-29 nuclear magnet ic resonance spectra and spin-lattice relaxation, at different magnetic fie lds, up to 15 T. For T greater than or equal to 200 K, an asymmetric centra l line with a satellite-like structure is observed, having a width linearly increasing with the field and a shift proportional to the magnetic suscept ibility. Below 200 K, a progressive broadening of the central line is detec ted on cooling, indicating an inhomogeneous distribution of local magnetiza tion. The spin-lattice relaxation, measured across the spectrum follows a l aw of the form T(1)(-1)proportional to (KT)-T-2, with K corresponding to th e shift of the different isocromates. The results are discussed in the ligh t of the spin-fluctuations theory for exchange-enhanced semiconductors. (C) 2000 American Institute of Physics. [S0021-8979(00)52608-5].