Critical Scaling of the Magnetization and Magnetostriction in the Weak Itinerant Ferromagnet UIr

TL;DR

This study investigates the critical magnetic behavior of the weak itinerant ferromagnet UIr, revealing unusual critical exponents and field-dependent magnetization and magnetostriction near the Curie temperature, extending up to several Tesla.

Contribution

It introduces a new method to extract uniaxial pressure dependences of $T_C$ and $M_s$ from magnetization and magnetostriction data in UIr, providing insights into spin fluctuations in anisotropic itinerant ferromagnets.

Findings

Critical behavior extends up to several Tesla at $T_C$

Critical exponents do not match known universality classes

Magnetization converges around 50 T at low temperature

Abstract

The weak itinerant ferromagnet UIr is studied by magnetization and magnetostriction measurements. Critical behavior, which surprisingly extends up to several Tesla, is observed at the Curie temperature $T_C\simeq45$ K and is analyzed using Arrott and Maxwell relations. Critical exponents are found that do not match with any of the well-known universality classes. The low-temperature magnetization $M_s\simeq0.5$ $\mu_B \cong const.$ below 3 T rises towards higher fields and converges asymptotically around 50 T with the magnetization at $T_C$. From the magnetostriction and magnetization data, we extract the uniaxial pressure dependences of $T_C$, using a new method presented here, and of $M_s$. These results should serve as a basis for understanding spin fluctuations in anisotropic itinerant ferromagnets.