Pr magnetism and its interplay with the Fe spin density wave in PrFeAsO

TL;DR

This study investigates the magnetic interactions between Pr3+ ions and Fe spin density wave in PrFeAsO, revealing how doping and magnetic fields influence crystal electric field levels, magnetic ordering, and spin canting phenomena.

Contribution

It provides new insights into the interplay between Pr magnetism and Fe magnetic order, highlighting the effects of doping and external magnetic fields on these interactions.

Findings

PrFeAsO exhibits a first CEF level at 3.5 meV, doped compound at 2.0 meV

Pr ordering causes anomalies in specific heat and thermal expansion

Field-induced transition involves reversal of Fe spin canting

Abstract

We have studied the magnetism of the Pr3+ ions in PrFeAsO_1-xF_x (x = 0; 0.15) and its interaction with the Fe magnetic order (for x = 0). Specific heat data confirm the presence of a first excited crystal electric field (CEF) level around 3.5 meV in the undoped compound PrFeAsO. This finding is in agreement with recent neutron scattering experiments. The doped compound is found to have a much lower first CEF splitting of about 2.0 meV. The Pr ordering in PrFeAsO gives rise to large anomalies in the specific heat and the thermal expansion coefficient. In addition, a field-induced transition is found at low temperatures that is most pronounced for the magnetostriction coefficient. This transition, which is absent in the doped compound, is attributed to a reversal of the Fe spin canting as the antiferromagnetic Pr order is destroyed by the external magnetic field.