Spin Fluctuations and the Magnetic Phase Diagram of ZrZn2

TL;DR

This paper investigates the magnetic behavior of ZrZn2, emphasizing the influence of quantum critical fluctuations on its properties and demonstrating how renormalized Landau theory can describe pressure effects.

Contribution

It introduces a renormalized Landau theory approach to account for quantum critical spin fluctuations in ZrZn2, improving understanding of its magnetic phase diagram.

Findings

Quantum critical fluctuations significantly affect ZrZn2's magnetization.

LDA calculations overestimate magnetization without considering fluctuations.

Pressure dependence of fluctuations can be described by a simple scaling law.

Abstract

The magnetic properties of the weak itinerant ferromagnet ZrZn_2 are analyzed using Landau theory based on a comparison of density functional calculations and experimental data as a function of field and pressure. We find that the magnetic properties are strongly affected by the nearby quantum critical point, even at zero pressure; LDA calculations neglecting quantum critical spin fluctuations overestimate the magnetization by a factor of approximately three. Using renormalized Landau theory, we extract pressure dependence of the fluctuation amplitude. It appears that a simple scaling based on the fluctuation-dissipation theorem provides a good description of this pressure dependence.