NMR studies of the incommensurate helical antiferromagnet EuCo2P2 : determination of the antiferromagnetic propagation vector

Recently Ding et al. [Phys. Rev. B 95, 184404 (2017)] reported that their nuclear magnetic resonance (NMR) study on EuCo$_2$As$_2$ successfully characterized the antiferromagnetic (AFM) propagation vector of the incommensurate helix AFM state, showing that NMR is a unique tool for determination of the spin structures in incommensurate helical AFMs. Motivated by this work, we have carried out $^{153}$Eu, $^{31}$P and $^{59}$Co NMR measurements on the helical antiferromagnet EuCo$_2$P$_2$ with an AFM ordering temperature $T_{\rm N}$ = 66.5 K. An incommensurate helical AFM structure was clearly confirmed by $^{153}$Eu and $^{31}$P NMR spectra on single crystalline EuCo$_2$P$_2$ in zero magnetic field at 1.6 K and its external magnetic field dependence. Furthermore, based on $^{59}$Co NMR data in both the paramagnetic and the incommensurate AFM states, we have determined the model-independent value of the AFM propagation vector k = (0, 0, 0.73 $\pm$ 0.09)2$\pi$/$c$ where $c$ is the $c$-axis lattice parameter. The temperature dependence of k is also discussed.Comment: 8 pages, 10 figures, accepted for publication in Phys. Rev. B. arXiv admin note: substantial text overlap with arXiv:1704.0629

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

Attempt to Generate Uniform Magnetic Field by Face-to-Face Magnet System Containing HTS Bulk Magnets

In order to develop small-scale nuclear magnetic resonance devices, the authors have been developing uniform magnetic fields in the space between the face-to-face settled magnetic poles which contain HTS bulk magnets. Since the NMR magnets in general require highly uniform field, it was expected to be difficult to form such homogeneous magnetic-field distribution with use of HTS bulk magnet, because the bulk magnets is characterized by its inhomogeneous magnetic field showing steep gradient. The authors modified the shape of the field distribution from convex to concave by attaching an iron plate on the pole surface. Then, the magnets were then settled face-to-face with various gaps, and the magnetic-field uniformity was estimated in the space. In order to detect the NMR signals, the field uniformity less than 1,500 ppm should be required after the former results on the hollow-type magnets. When we combined the concave and convex field distributions to compensate the uneven field distributions, the best uniformity reached 358 ppm in the 30 mm gaps, which exceeded the target value. In addition, we numerically simulated the feasible performance in this configuration, which resulted in obtaining the best uniformity of 30 ppm at 1.1 T at 7 mm distant from the pole surface in the gap of 30 mm. This result suggested that the concave and convex magnetic field distributions compensate the field uniformity with each other with keeping the magnetic field strength in the gap

琉球列島の西表島で蛙の鳴き声トラップに誘引された蚊類について

金沢大学留学生センター2004年6月12-18日に, 琉球列島の西表島の森林地帯の2ヵ所で, 蛙の声をCDプレイヤーで鳴らし, 直ぐ近くにCDCライトトラップを設置し蚊類を採集した.第一地点で合計777個体, 2地点で257個体のハエ目の昆虫が採集された.それらのうち, 次の4種の吸血性昆虫(雌)が両地点で目立って多く採集された.マックファレンチビカは第一地点で580個体(74.6%), 第二地点で193 (75.1), ヤエヤマカニアナチビカ19(2.4)と27 (10.5), ヤマトケヨソイカ106 (13.6)と20(7.8), また, ルソンコブハシカが第一地点のみで39個体(5.0%)が採集された.これらの蚊にケージ内でヌマガエルを暴露すると, 吸血行動が見られ, 多くの個体が吸血した.このことからこれらの蚊は自然界でカエルの鳴き声に誘引され, 吸血していると思われる. Mosquito collections were made at two foothill sites of Iriomote Island, the Ryukyu Archipelago, Japan, by modified CDC miniature light traps with a frog call CD player from June 12 to 18, 2004. A total of 777 and 257 female Diptera was collected at sites 1 and 2, respectively. Among them, 4 haematophagous species were predominant at sites 1 and 2-Uranotaenia macfarlanei with 580 (74.6%) and 193 (75.1%) individuals respectively, Ur. yaeyamana 19 (2.4%) and 27 (10.5%), and Corethrella nippon 106 (13.6%) and 20 (7.8%) which is a new record for Iriomote Island, and Mimomyia luzonensis with 39 (5.0%) individuals was predominant at site 1. The females of these species collected by the traps fed easily on a frog, Rana limnocharis exposed in the cage. The results demonstrated clearly that frog call is the primary stimulus in guiding these Culicine and Chaoborine flies in their search for host animals in nature