Magnetic Phase Diagram of YbRh\textsubscript{2}Si\textsubscript{2}: the Influence of Hyperfine Interactions

TL;DR

This study maps the complex magnetic phase diagram of YbRh₂Si₂, revealing how hyperfine interactions influence quantum phase transitions and the coexistence of magnetic orders in this heavy fermion system.

Contribution

It provides the first detailed phase diagram of YbRh₂Si₂ considering hyperfine interactions, extending measurements into the microkelvin regime.

Findings

Identification of two antiferromagnetic phases, AFM1 and AFM2.

Hyperfine interactions significantly alter the phase diagram.

Observation of quantum phase transitions at ultra-low temperatures.

Abstract

We report the determination of the magnetic phase diagram of the heavy fermion metal YbRh\textsubscript{2}Si\textsubscript{2} in magnetic fields up to 70\,mT applied perpendicular to the crystallographic c-axis. By a combination of heat capacity, magneto-caloric, and magneto-resistance measurements we map two antiferromagnetic phases: the electronic AFM1 below 70\,mK and electro-nuclear AFM2 below 1.5\,mK. The measurements extend into the microkelvin regime to explore the quantum phase transitions in this system. We demonstrate how the hyperfine interaction significantly modifies the phase diagram and the putative field-tuned quantum critical point. The determination of the rich magnetic properties of YbRh\textsubscript{2}Si\textsubscript{2} is essential to understanding the interplay of the two magnetic orders and superconductivity in this compound.