Field Induced Modulated State in the Ferromagnet PrPtAl

TL;DR

This study investigates the field-induced modulated magnetic state in PrPtAl, demonstrating that quantum order-by-disorder theory explains the emergence of a fan state under magnetic field, supported by resistivity and neutron scattering data.

Contribution

The paper provides experimental phase diagrams and evidence supporting QOBD theory as the mechanism behind field-induced modulated states in PrPtAl.

Findings

Identification of a field-induced fan state in PrPtAl

Large increase in resistivity T^2 coefficient across the fan state

Enhanced magnetic fluctuations detected by neutron scattering

Abstract

The theory of quantum order-by-disorder (QOBD) explains the formation of modulated magnetic states at the boundary between ferromagnetism and paramagnetism in zero field. PrPtAl has been argued to provide an archetype for this. Here, we report the phase diagram in magnetic field, applied along both the easy $a$-axis and hard $b$-axis. For field aligned to the $b$-axis, we find that the magnetic transition temperatures are suppressed and at low temperature there is a single modulated fan state, separating an easy $a$-axis ferromagnetic state from a field polarised state. This fan state is well explained with the QOBD theory in the presence of anisotropy and field. Experimental evidence supporting the QOBD explanation is provided by the large increase in the $T^2$ coefficient of the resistivity and direct detection of enhanced magnetic fluctuations with inelastic neutron scattering, across the field range spanned by the fan state. This shows that the QOBD mechanism can explain field induced modulated states that persist to very low temperature.