Anomalous magnetic phase diagram in low-carrier two-band systems and possible application to CeOs4Sb12

TL;DR

This paper investigates magnetic phase diagrams in low-carrier two-band systems, explaining anomalous phase boundaries observed in materials like CeOs4Sb12 through theoretical models and susceptibility calculations.

Contribution

It introduces a theoretical analysis of magnetic phase boundaries in low-carrier two-band systems, linking them to experimental observations in CeOs4Sb12.

Findings

Magnetic susceptibility peaks are enhanced perpendicular to the external field.

Phase boundary shifts to higher temperatures under magnetic field in insulating states.

Similar phase boundary features appear in semi-metallic states due to density of states structure.

Abstract

Magnetic properties under the external field are investigated in low-carrier two-band systems, which may explain the nontrivial phase boundary found in temperature vs. magnetic field diagram discovered in some materials, such as filled-skutterudite compound CeOs$_{4}$Sb$_{12}$. Analysis is made both for the periodic Anderson model with the small-dispersive $f$ band and the simplified two parabolic band model in the vicinity of the Fermi level. The magnetic susceptibilities are calculated by using the random phase approximation. It is shown that the maximum value of the magnetic susceptibility perpendicular to the external field is enhanced and yields the anomalous phase boundary. By applying the magnetic field, the phase boundary shifts to higher temperature region in the insulating state with a small band gap. On the other hand, the similar phase boundary also appears in the semi-metallic states, in which the structure of the density of states in the vicinity of the Fermi level and the finite temperature effect are essential.