Accurate Investigation of Effects of Band Structure and Matrix Element on the Magnetic Susceptibility

抄録

Effects of band structure and matrix element on the magnetic susceptibility defined as the Fourier transform of RKKY interaction are investigated accurately assuming the simple band model, and the validity of the free electron model is also examined. The following points are verified from the numerical calculations. When the Fermi surface has sections perpendicular to the vector q, in which q is an argument in the susceptibility, the strength of the Kohn anomaly is largely modified by the matrix element, which can be replaced by the values at the states on the Fermi surface causing the anomaly. When the Fermi surface has no sections perpendicular to q, the replacement cannot be allowed and their integration is important, and therefore it may be difficult to predict the matrix element effect. When the free electron Fermi sphere is completely contained in the Brillouin zone and is sufficiently away from a zone boundary, the free electron approximation is still rather good, although the effects of the Kohn anomalies and the matrix elements can be seen. But, when the sphere extends into other zones, since it is cut at the zone boundaries into some parts, the dispersion of the susceptibility becomes very much complicated by the presence of many Kohn anomalies, and can be also changed further drastically by the matrix element effect.