Soliton lattice structure of incommensurate spin-density waves: Application to Cr and Cr-rich Cr-Mn and Cr-V alloys

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Abstract
Based on the two-band imperfect-nesting model within the mean-field approximation, the incommensurate spin-density wave (ISDW) is investigated theoretically. Taking into account infinite numbers of higher harmonics, we obtain an exact solution under the assumptions that the electron dispersion relation is linearized near the Fermi level and that the ISDW is characterized by a single wave vector. The exact solution which describes the snoidal-wave modulation of the ISDW gives rise to the mid-gap state in the density of states. We successfully explain various experimental data on Cr and Cr-rich Cr-Mn and Cr-V alloys in a consistent manner, including phase diagram, the alloying and temperature dependences of the wave number, the higher-order satellite intensities in neutron experiments, and saturation moments. In particular, the two-energy-gap structure in Cr detected by an optical measurement is interpreted as a direct manifestation of the mid-gap state associated with the soliton lattice nature of the snoidal solution.