Imaging the magnetic states in an actinide ferromagnet UMn2Ge2

Abstract

We present studies of the magnetic domain structure of UMn2Ge2 single crystals using a homebuilt 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 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 flower-like pattern reveals that the domain structure is consistent with a model of branching domains. PACS numbers: May be entered using the \pacs{#1} command.

Extreme narrow magnetic domain walls in U ferromagnets: The UCoGa case

“…The direct imaging and investigation of domain structures in U compounds have been done on polycrystalline samples at room temperature (RT) in materials with a high concentration of 3d transition metals [23,24] with magnetic moments which are ferromagnetically coupled by strong EI resulting in high TC-values (>> RT). The only report on the single crystalline material containing uranium has been recently published [25] on the UMn2Ge2. Although this material has comparable [26] anisotropy (roughly ¼) in comparison to the compound under study [27], the formation of magnetic domains is determined by the ordering of Mn moment at higher (above RT) temperatures.…”