Spin-density-wave antiferromagnetism in the chromium system I: magnetic phase diagrams, impurity states, magnetic excitations and structure in the SDW phase

摘要

The chromium system, comprising pure Cr and alloys with most transition metals and some non-transition metals, is the archetypical spin-density-wave (SDW) system. This paper supplements, with a brief summary and extension to include recent work, two previous comprehensive reviews on Cr (Fawcett, 1988) and Cr alloys (Fawcett et al., 1994). The magnetic phase diagrams are reviewed. Impurity states in CrFe and CrSi, when suitable doped with V or Mn, produce dramatic effects in the electrical resistivity, including a low-temperature resistance minimum due to impurity-rsonance scattering. Curie-Weiss paramagnetism appears just above the Neel temperature in dilute CrV alloys. Recent work on inelastic netron scattering in pure Cr is revewed: the apparent absence of dispersion of the spin-wave modes at the wave vectors of the incommensurate SDW where the Bragg stellite peaks occur; the energy-dependent anisotropy of the excitations in the longitudinal-SDW phase; the commensurate magnetic scatterin at the centre of the magnetic the Fincher-Rurke excitations seen at low-energy in the transverse-SDW phase; and the silent satellites seen in sinlge-Q Cr at off-axis incommensurate points as temperature increases towards the Neel transition. X-ray scattering with synchrotron radiation has illuminated the relation between the SDW in Cr and the incommensurate charge-density wave that accompanies it.