Magnetic Properties of Sinusoidal Spin-Density Waves by the Band Model

Abstract

Various properties of the sinusoidal spin‐density waves observed in Cr are explained by the band model of a magnetic medium. By the method proposed before, the increase of the free‐energy density due to a given distribution of the magnetization 2μ_Bn(r) is written as a function of temperature, magnetic field, n(r) and its derivatives. In order to get a stable sinusoidal modulation of a simple antiferromagnetic ordering, the ordinary and higher‐order exchange stiffness constants in the expansion of magnetic energy as a power series of n(r) and its derivatives are expected to be negative and positive, respectively. New interaction energies between elastic strains and derivatives of n(r), besides the ordinary magnetoelastic energy, are introduced in our model to explain the transition between transversal and longitudinal SSDW's and the anisotropies, relative to the directions of modulation and polarization, of the susceptibility and dilatation; the nature of the transition at the Néel temperature is also discussed. The temperature variations of the maximum moment of SSDW, specific heat, and susceptibility are calculated by our model. From the comparison between these calculated and experimental results it will be seen that our model of SSDW is very useful to explain various properties of the SSDW observed in Cr metal.