Helicity Selection of the Cycloidal Order in Noncentrosymmetric EuIrGe3_3

The magnetic helicities of the cycloidal ordering in EuIrGe$_3$, with a noncentrosymmetric tetragonal structure, have been studied by circularly polarized resonant X-ray diffraction. It is shown that the helicity of each cycloidal domain is uniquely determined and satisfies the symmetry relations of the $C_{4v}$ point group of the crystal structure. The result shows that the cycloidal helicity is determined by the Dzyaloshinskii-Moriya type antisymmetric exchange interaction. The domain selection and the phase transition by the external magnetic field along [100] and [110] have also been studied. It is shown that the cycloidal plane prefers to be perpendicular to the field and the transverse conical state is realized.Comment: 6 pages, 4 figures, 5 figures in the supplemental material, accepted for publication in J. Phys. Soc. Jp

CO oxidation on perovskite-type LaCoO3 synthesized using ethylene glycol and citric acid

In order to synthesize perovskite-type LaCoO3 with good surface crystallinity, the gel prepared by adding both ethylene glycol (EG) and citric acid (CA) to the aqueous solution of La(NO3)3 center dot 6H(2)O and Co(NO3)(2) center dot 6H(2)O was fired at 600 degrees C in air for 3 h. The transmission electron microscopy (TEM) observation indicated that the particles of LaCoO3 tended to have a uniform shape at EG/CA = 4. Although, the specific surface area of LaCoO3 synthesized using both EG and CA was slightly smaller than that of LaCoO3 synthesized using only CA, the catalytic activity of CO oxidation became higher by adding EG

Pressure Effect on Transport Properties of EuNi(Si1-xGex)3 Compounds

AbstractThe compounds of EuNi(Si1−xGex)3 order antiferromagnetically. At the temperature TC below the Ńeel temperature TN, EuNiSi3 (x = 0) shows an additional magnetic transition into ferro-magnetic state. TN decreases monotonously with increasing the Ge composition x. The Curie temperature TC decreases rapidly with increasing x and vanishes at the critical composition x ≈ 0.3. We have measured the electrical resistivity and thermopower of EuNi(Si0.8Ge0.2)3, which is a compound near to the boundary between the ferromagnetic and antiferromagnetic ground states in the phase diagram for EuNi(Si1−xGex)3 system, under pressures up to 1.8GPa at temperatures from 2 to 300K. The anomalies in ρ(T) and S(T) curves of EuNi(Si0.8Ge0.2)3 are observed at TC = 16K and TN = 34K at ambient pressure. Both TC and TN increase linearly with increasing pressure. The temperature variations of ρ and S of EuNi(Si0.8Ge0.2)3 at P = 1.8GPa are almost the same as those of EuNi(Si0.9Ge0.1)3 (x=0.1) at ambient pressure, revealing that the effect of pressure on TN and TC is the same as that of the increase of Si concentration. The pressure and atomic composition dependences of the magnetic transition temperatures TN and TC can be expressed by using the Grüneisen parameters. These results indicate that the changes of TN and TC are attributed to the change of atomic volume induced by the applying pressure or the atomic substitution

Magnetic Field Induced Triple-q Magnetic Order in Trillium Lattice Antiferromagnet EuPtSi Studied by Resonant X-ray Scattering

Magnetic order in the magnetic-field-induced so-called A phase of cubic chiral antiferromagnet EuPtSi was investigated by resonant X-ray scattering (RXS) near the Eu L2 absorption edge. The high-intensity RXS signal revealed the triple-q magnetic order of the A phase in a magnetic field applied along the [111] direction. The triple-q order is described by three propagation vectors lying on the plane normal to the magnetic field direction. The triple-q magnetic order is discussed in the context of a magnetic skyrmion lattice where geometrical frustration may play a crucial role