Crystal and magnetic structures of Cr1/3NbSe2 from neutron diffraction

Under a Creative Commons Attribution (CC BY) license.-- et al.Neutron diffraction measurements of the Cr intercalated niobium diselenide CrNbSe together with magnetization measurements have revealed that this compound exhibits ferromagnetic ordering below T = 96 K unlike a chiral helimagnetic order observed in the sulfide compound CrNbS. As derived from neutron diffraction data, the Cr magnetic moments μ = 2.83 ± 0.03 μ in CrNbSe are aligned within basal plane. The discrepancy in the magnetic states of CrNbS and CrNbSe is ascribed to the difference in the preferential site occupation of Cr ions in crystal lattices. In CrNbSe, the Cr ions are predominantly distributed over 2b Wyckoff site, which determines a centrosymmetric character of the crystal structure unlike CrNbS, where the Cr ions are mainly located in 2c position and the crystal structure is non-centrosymmetric.This work is partly based on experiments performed at the Japan Proton Accelerator Research Complex J-PARC. This work was performed within the state assignment of the FASO of Russia (No. 01201463334) and supported by Act 211 Government of the Russian Federation (Contract No. 02.A03.21.0006), by the Russian Foundation for Basic Research (Project Nos. 13-02-00364 and 13-02-92104), by the program of UB of RAS (Project No. 15-17-2-22), and by Grants-in-Aid for Scientific Research (Nos. 25220803, 242440590, and 25246006) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. This work was also supported by the Center for Chiral Science in Hiroshima University (the MEXT program for promoting the enhancement of research universities, Japan) and JSPS Core-to-Core Program, A. Advanced Research Networks. J.C. and Y.K. acknowledge the Grant No. MAT2011-27233-C02-02.Peer Reviewe

Interlayer magnetoresistance due to chiral soliton lattice formation in hexagonal chiral magnet CrNb3S6

We investigate the interlayer magnetoresistance (MR) along the chiral crystallographic axis in the hexagonal chiral magnet CrNb3S 6. In a region below the incommensurate-commensurate phase transition between the chiral soliton lattice and the forced ferromagnetic state, a negative MR is obtained in a wide range of temperature, while a small positive MR is found very close to the Curie temperature. Normalized data of the negative MR almost falls into a single curve and is well fitted by a theoretical equation of the soliton density, meaning that the origin of the MR is ascribed to the magnetic scattering of conduction electrons by a nonlinear, periodic, and countable array of magnetic soliton kinks. © 2013 American Physical Society

Tensile deformations of the magnetic chiral soliton lattice probed by Lorentz transmission electron microscopy

We consider the case of a chiral soliton lattice subjected to uniaxial elastic strain applied perpendicular to the chiral axis and derive through analytical modeling the phase diagram of magnetic states supported in the presence of an external magnetic field. The strain induced anisotropies give rise to three distinct nontrivial spin textures, depending on the nature of the strain, and we show how these states may be identified by their signatures in Lorentz transmission electron microscopy (TEM). Experimental TEM measurements of the Fresnel contrast in a strained sample of the prototypical monoaxial chiral helimagnet CrNb3S6 are reported and compare well with the modeled contrast. Our results demonstrate an additional degree of freedom that may be used to tailor the magnetic properties of helimagnets for fundamental research and applications in the areas of spintronics and the emerging field of strain manipulated spintronics. © 2020 American Physical Society.This work was supported by a Grants-in-Aid for Scientific Research (B) (KAKENHI Grants No.17H02767 and No. 17H02923) from the MEXT of the Japanese Government, JSPS Bilateral Joint Research Projects (JSPS-FBR), the JSPS Core-to-Core Program, A. Advanced Research Networks, the Engineering and Physical Sciences Research Council (EPSRC) of the U.K. under Grant No. EP/M024423/1, and Grants-in-Aid for Scientific Research on Innovative Areas “Quantum Liquid Crystals” (KAKENHI Grant No. JP19H05826) from JSPS of Japan. I.P. and A.A.T. acknowledge financial support by the Ministry of Education and Science of the Russian Federation, Grant No. MK-1731.2018.2 and by the Russian Foundation for Basic Research (RFBR), Grant No. 18-32-00769 (mol_a). A.S.O. and A.A.T. acknowledge funding by the Foundation for the Advancement of Theoretical Physics and Mathematics BASIS Grant No. 17-11-107, and by Act 211 Government of the Russian Federation, Contract No. 02.A03.21.0006. A.S.O. thanks the Russian Foundation for Basic Research (RFBR), Grant 20-52-50005, and the Ministry of Education and Science of Russia, Project No. FEUZ-2020-0054

Crystal and magnetic structures of Cr1/3NbSe2 from neutron diffraction

Neutron diffraction measurements of the Cr intercalated niobium diselenide Cr1/3NbSe2 together with magnetization measurements have revealed that this compound exhibits ferromagnetic ordering below TC = 96 K unlike a chiral helimagnetic order observed in the sulfide compound Cr1/3NbS2. As derived from neutron diffraction data, the Cr magnetic moments µCr = 2.83 ± 0.03 µB in Cr1/3NbSe2 are aligned within basal plane. The discrepancy in the magnetic states of Cr1/3NbS2 and Cr1/3NbSe2 is ascribed to the difference in the preferential site occupation of Cr ions in crystal lattices. In Cr1/3NbSe2, the Cr ions are predominantly distributed over 2b Wyckoff site, which determines a centrosymmetric character of the crystal structure unlike Cr1/3NbS2, where the Cr ions are mainly located in 2c position and the crystal structure is non-centrosymmetric

Collective resonant dynamics of the chiral spin soliton lattice in a monoaxial chiral magnetic crystal

The magnetic resonance properties of microsized monoaxial chiral crystals of CrNb3S6 are investigated. We observed that the resonance of the chiral soliton lattice is sensitive to the polarization of the driving microwave field. When the microwave field is parallel to the helical axis, the resonance is symmetric with regards to the magnetic field direction. In contrast, asymmetric field dependence emerges when the microwave field is perpendicular to the helical axis. The robustness of the chiral magnetic order, due to topological protection, allows tuning the resonance frequency in ways hardly accessible using nanopatterned films

Extensive Transcriptional Regulation of Chromatin Modifiers during Human Neurodevelopment

Epigenetic changes, including histone modifications or chromatin remodeling are regulated by a large number of human genes. We developed a strategy to study the coordinate regulation of such genes, and to compare different cell populations or tissues. A set of 150 genes, comprising different classes of epigenetic modifiers was compiled. This new tool was used initially to characterize changes during the differentiation of human embryonic stem cells (hESC) to central nervous system neuroectoderm progenitors (NEP). qPCR analysis showed that more than 60% of the examined transcripts were regulated, and >10% of them had a >5-fold increased expression. For comparison, we differentiated hESC to neural crest progenitors (NCP), a distinct peripheral nervous system progenitor population. Some epigenetic modifiers were regulated into the same direction in NEP and NCP, but also distinct differences were observed. For instance, the remodeling ATPase SMARCA2 was up-regulated >30-fold in NCP, while it remained unchanged in NEP; up-regulation of the ATP-dependent chromatin remodeler CHD7 was increased in NEP, while it was down-regulated in NCP. To compare the neural precursor profiles with those of mature neurons, we analyzed the epigenetic modifiers in human cortical tissue. This resulted in the identification of 30 regulations shared between all cell types, such as the histone methyltransferase SETD7. We also identified new markers for post-mitotic neurons, like the arginine methyl transferase PRMT8 and the methyl transferase EZH1. Our findings suggest a hitherto unexpected extent of regulation, and a cell type-dependent specificity of epigenetic modifiers in neurodifferentiation