Microscopic Theory of Magnetic Phase Transitions in HoNi_2B_2C

TL;DR

This paper develops a microscopic theory explaining the magnetic phase transitions in HoNi_2B_2C, aligning well with experimental data and revealing the interplay of crystal field effects and RKKY interactions without involving superconductivity.

Contribution

It provides a detailed microscopic model for the magnetic phases of HoNi_2B_2C, including the temperature-dependent ground state and phase transitions, based on fundamental interactions.

Findings

The theory matches experimental phase diagrams.

Identifies the competition between crystal field and RKKY interactions as key.

Explains the c-axis transition behavior without superconductivity influence.

Abstract

We present a microscopic theory for the low temperature metamagnetic phase diagram of HoNi_2B_2C that agrees well with experiments.For the same model we determined the zero field ground state as a function of temperature and find the $c$-axis commensurate to incommensurate transition in the expected temperature range. The complex behaviour of the system originates from the competition between the crystalline electric field and the Ruderman-Kittel-Kasuya-Yosida interaction, whose effective form is obtained. No essential influence of superconductivity has to be invoked to understand the magnetic phase diagram of this material.