Imaging the magnetic states in an actinide ferromagnet UMn2Ge2

Abstract

We present studies of the magnetic domain structure of UMn2Ge2 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 flowerlike domain patterns similar to those observed in uniaxial ferromagnets. After exposing the sample to a 1 T magnetic field near 40 K, the evolution of the magnetic domains are imaged through zero-field warming up to 210 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 flowerlike pattern reveals that the domain structure is consistent with a model of branching domains.