Theoretical model for the superconducting and magnetically ordered borocarbides

TL;DR

This paper develops a theoretical framework to understand the interplay of superconductivity and complex magnetic orders in borocarbides, explaining phenomena like reentrant behavior and anisotropic critical fields.

Contribution

It introduces a comprehensive theory for superconductivity coexisting with magnetic structures in borocarbides, incorporating band structure details and magnetic phase diagrams.

Findings

Explains reentrant superconductivity behavior in HoNi2B2C.

Accounts for anisotropy of the upper critical magnetic field.

Shows magnetic order reduces electron-phonon interactions, affecting superconductivity.

Abstract

We present a theory of superconductivity in presence of a general magnetic structure in a form suitable for the description of complex magnetic phases encountered in borocarbides. The theory, complemented with some details of the band structure and with the magnetic phase diagram, may explain the nearly reentrant behaviour and the anisotropy of the upper critical field of HoNi2B2C. The onset of the helical magnetic order depresses superconductivity via the reduction of the interaction between phonons and electrons caused by the formation of magnetic Bloch states. At mean field level, no additional suppression of superconductivity is introduced by the incommensurability of the helical phase.