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Characterization of low-energy magnetic excitations in chromium

H. Hiraka·P. Boni·K. Yamada·S. Park·S-. H. Lee·G. Shirane
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Abstract

The low-energy excitations of Cr, i.e. the Fincher-Burke (FB) modes, have been investigated in the transversely polarized spin-density-wave phase by inelastic neutron scattering using a single-(Q+-) crystal with a propagation vector (Q+-) parallel to [0,0,1]. The constant-momentum-transfer scans show that the energy spectra consist of two components, namely dispersive FB modes and an almost energy-independent cross section. Most remarkably, we find that the spectrum of the FB modes exhibits one peak at 140 K near Q = (0,0,0.98) and two peaks near Q = (0,0,1.02), respectively. This is surprising because Cr crystallizes in a centro-symmetric bcc structure. The asymmetry of those energy spectra decreases with increasing temperature. In addition, the observed magnetic peak intensity is independent of Q suggesting a transfer of spectral-weight between the upper and lower FB modes. The energy-independent cross section is localized only between the incommensurate peaks and develops rapidly with increasing temperature.

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H. Hiraka, P. Boni, K. Yamada, S. Park, S-. H. Lee, G. Shirane. 2003-12-16. Characterization of low-energy magnetic excitations in chromium. https://doi.org/10.1103/physrevb.70.144413

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