Anisotropic physical properties of single crystal U2Rh2Sn in high magnetic fields

We report on the crystal and magnetic structures,magnetic, transport, and thermal properties of U2Rh2Sn single crystals studied in part in high magnetic fields up to 58 T. The material adopts a U3Si2 related tetragonal crystal structure and orders antiferromagnetically below TN 25 K. The antiferromagnetic structure is characterized by a propagation vector k 0,0,1 2 . The magnetism in U2Rh2Sn is found to be associated mainly with 5f states. However, both unpolarized and polarized neutron experiments reveal at low temperatures in zero field non negligible magnetic moments also on Rh sites. U moments of 0.50 2 amp; 956;B are directed along the tetragonal axis while Rh moments of 0.06 4 amp; 956;B form a noncollinear arrangement confined to the basal plane. The response to applied magnetic field is highly anisotropic. Above amp; 8764;15 K the easy magnetization direction is along the tetragonal axis. At lower temperatures, however, a stronger response is found perpendicular to the c axis. While for the a axis no magnetic phase transition is observed up to 58 T, for the field applied at 1.8 K along the tetragonal axis we observe above 22.5 T a field polarized state. A magnetic phase diagram for the field applied along the c axis is presented

Emergent 1/3 magnetization plateaus in pyroxene CoGeO3

Despite the absence of an apparent triangular pattern in the crystal structure, we observe unusually well-pronounced 1/3 magnetization plateaus in the quasi-one-dimensional Ising spin chain compound CoGeO3 which belongs to the class of pyroxene minerals. We succeeded in uncovering the detailed microscopic spin structure of the 1/3 magnetization plateau phase by means of neutron diffraction. We observed changes of the initial antiferromagnetic zero-field spin structure that resemble a regular formation of antiferromagnetic domain wall boundaries, resulting in a kind of modulated magnetic structure with a 1/3-integer propagation vector. The net ferromagnetic moment emerges at these domain walls whereas two thirds of all antiferromagnetic chain alignments can be still preserved. We propose a microscopic model on the basis of an anisotropic frustrated square lattice to explain the observations

Single-crystal investigations on the multiferroic material LiFe(WO4)(2)

The crystal and magnetic structures of multiferroic LiFe(WO4)(2) were investigated by temperature and magnetic-field-dependent specific heat, susceptibility, and neutron diffraction experiments on single crystals. Considering only the two nearest-neighbor magnetic interactions, the system forms a J(1), J(2) magnetic chain, but more extended interactions are sizable. Two different magnetic phases exhibiting long-range incommensurate order evolve at T-N1 approximate to 22.2 K and T-N2 approximate to 19 K. First, a spin-density wave develops with moments lying in the ac plane. In its multiferroic phase below T-N2 LiFe(WO4)(2) exhibits a spiral arrangement with an additional spin component along b. Therefore, the inverse Dzyaloshinskii-Moriya mechanism fully explains the multiferroic behavior in this material. A partially unbalanced multiferroic domain distribution was observed even in the absence of an applied electric field. For both phases only a slight temperature dependence of the incommensurability was observed, and there is no commensurate phase emerging at low temperature or at finite magnetic fields up to 6 T. LiFe(WO4)(2) thus exhibits a simple phase diagram with the typical sequence of transitions for a type-II multiferroic material