Imaging the magnetic states in an actinide ferromagnet UMn$_2$Ge$_2$

TL;DR

This study uses magnetic force microscopy to image and analyze the magnetic domain structures in UMn$_2$Ge$_2$, revealing temperature-dependent domain evolution related to its dual magnetic ordering temperatures.

Contribution

The paper provides the first detailed imaging of magnetic domains in UMn$_2$Ge$_2$, highlighting the temperature-dependent domain evolution associated with Mn and U magnetic moments.

Findings

Flower-like domain patterns at room temperature dominated by Mn moments

Domain evolution observed near uranium ordering temperature

Domain structure consistent with branching domain model

Abstract

We present studies of the magnetic domain structure of UMn$_2$Ge$_2$ single crystals using a home-built low temperature magnetic force microscope. The material has two distinct magnetic ordering temperatures, originating from the Mn and U moments. At room temperature, where the Mn moments dominate, there are flower-like domain patterns similar to those observed in uniaxial ferromagnets. After exposing the sample to a one-tesla magnetic field near 40 K, the evolution of the magnetic domains are imaged through zero-field warming up to 200 K. Near the ordering temperature of the uranium moments a clear change in the domain wall motion is observed. The domain size analysis of the flower-like pattern reveals that the domain structure is consistent with a model of branching domains.