Quarter Magnetization Plateau of Triplet Spin Dimers in the Shastry-Sutherland Lattice

The Shastry-Sutherland lattice, 2-dimensional orthogonal arrangement of the spin dimers, has been realized in the magnetic semiconductor, BaNd2ZnS5. A signature feature of Shastry-Sutherland lattice materials is fractional magnetization plateaus, which often indicate novel quantum phases. Here we report the quarter magnetization plateau from a single crystal of BaNd2ZnS5 by neutron diffraction. A 2-Q antiferromagnetic order of the triplet spin dimers was determined at zero-field, which can be understood by the local Ising magnetic anisotropy of Nd spins that was revealed by local magnetic susceptibility method through polarized neutron diffraction. The quantized magnetization plateau was measured under field along (1-10). The two magnetic sublattices connected to each propagation vector of 2-Q respond to the field differently, the stripe phase with q1 = (0.5, 0.5, 0) disappears at ~1.7 T entering the quarter magnetization plateau. The other stripe phase with q2= (-0.5, 0.5, 0) remains nearly intact up to 6 T. Furthermore, microscopic magnetic model was used to provide insight into the formation of quarter magnetization plateau, that is unexpected in gapless dimer triplet system, contrast to the well-known dimer-singlet Shastry-Sutherland lattice.Comment: 15 pages, 4 figure

Γ-brasses in the Mn-Zn system: An experimental and computational study

The synthesis and characterization of Ni2Zn11-type γ-brasses with composition Mn2+xZn11−x (x = 0.06–0.60) are reported. The synthesis follows standard high temperature methods and characterization by single crystal X-ray diffraction (SCXRD) and powder X-ray Diffraction (PXRD) techniques as well as Energy Dispersive Spectroscopy (EDS). First principles electronic structure calculations showed preferential heteroatomic Mn–Zn bonding and repulsive effects of Zn–Zn 3d–3d orbital overlap that influence the metal atom distribution in the structure. Local bonding environments and the relationship of Mn2+xZn11-x to other γ-brasses containing 3d metals such as PdCoZn11 and Ni2Zn11 are discussed

Annihilation and Control of Chiral Domain Walls with Magnetic Fields

The control of domain walls is central to nearly all magnetic technologies, particularly for information storage and spintronics. Creative attempts to increase storage density need to overcome volatility due to thermal fluctuations of nanoscopic domains and heating limitations. Topological defects, such as solitons, skyrmions, and merons, may be much less susceptible to fluctuations, owing to topological constraints, while also being controllable with low current densities. Here, we present the first evidence for soliton/soliton and soliton/antisoliton domain walls in the hexagonal chiral magnet Mn1/3NbS2 that respond asymmetrically to magnetic fields and exhibit pair-annihilation. This is important because it suggests the possibility of controlling the occurrence of soliton pairs and the use of small fields or small currents to control nanoscopic magnetic domains. Specifically, our data suggest that either soliton/soliton or soliton/antisoliton pairs can be stabilized by tuning the balance between intrinsic exchange interactions and long-range magnetostatics in restricted geometriesComment: 8 pages, 4 figure

Tiny Sc allows the chains to rattle: Impact of Lu and Y doping on the charge density wave in ScV6_6Sn6_6

The kagome metals display an intriguing variety of electronic and magnetic phases arising from the connectivity of atoms on a kagome lattice. A growing number of these materials with vanadium kagome nets host charge density waves (CDWs) at low temperatures including ScV$_6$Sn$_6$, CsV$_3$Sb$_5$, and V$_3$Sb$_2$. Curiously, only the Sc version of the $R$V$_6$Sn$_6$ HfFe$_6$Ge$_6$-type materials hosts a CDW ($R =$Gd-Lu, Y, Sc). In this study we investigate the role of rare earth size in CDW formation in the $R$V$_6$Sn$_6$ compounds. Magnetization measurements on our single crystals of (Sc,Lu)V$_6$Sn$_6$ and (Sc,Y)V$_6$Sn$_6$ establish that the CDW is suppressed by substitution of Sc by larger Lu or Y. Single crystal x-ray diffraction reveals that compressible Sn-Sn bonds accommodate the larger rare earth atoms within loosely packed $R$-Sn-Sn chains without significantly expanding the lattice. We propose that Sc provides the extra room in these chains crucial to CDW formation in ScV$_6$Sn$_6$. Our rattling chain model explains why both physical pressure and substitution by larger rare earths hinder CDW formation despite opposite impacts on lattice size. We emphasize the cooperative effect of pressure and rare earth size by demonstrating that pressure further suppresses the CDW in a Lu-doped ScV$_6$Sn$_6$ crystal. Our model not only addresses why a CDW only forms in the $R$V$_6$Sn$_6$ materials with tiny Sc, it also advances to our understanding of why unusual CDWs form in the kagome metals.Comment: 28 pages, 9 figures, crystallographic information files for LuV6Sn6 and YV6Sn6 along with supplemental materials in ancillary file

Γ-brasses in the Mn-Zn system: An experimental and computational study

The synthesis and characterization of Ni2Zn11-type γ-brasses with composition Mn2+xZn11−x (x = 0.06–0.60) are reported. The synthesis follows standard high temperature methods and characterization by single crystal X-ray diffraction (SCXRD) and powder X-ray Diffraction (PXRD) techniques as well as Energy Dispersive Spectroscopy (EDS). First principles electronic structure calculations showed preferential heteroatomic Mn–Zn bonding and repulsive effects of Zn–Zn 3d–3d orbital overlap that influence the metal atom distribution in the structure. Local bonding environments and the relationship of Mn2+xZn11-x to other γ-brasses containing 3d metals such as PdCoZn11 and Ni2Zn11 are discussed.</p

New Tetragonal ReGa5(M) (M = Sn, Pb, Bi) Single Crystals Grown from Delicate Electrons Changing

Single crystals of the new Ga-rich phases ReGa~5(Sn), ReGa~5(Pb) and ReGa~5(Bi) were successfully obtained from the flux method. The new tetragonal phases crystallize in the space group P4/mnc (No. 128) with vertex-sharing capped Re2@Ga14 oblong chains. Vacancies were discovered on the Ga4 and Ga5 sites, which can be understood as the direct inclusion of elemental Sn, Pb and Bi into the structure. Heat capacity measurements were performed on all three compounds resulting in a small anomaly which resembles the superconductivity transition temperature from the impurity ReGa5 phase. The three compounds were not superconducting above 1.85 K. Subsequently, electronic structure calculations revealed a high density of states around the Fermi level, as well as non-bonding interactions that likely indicate the stability of these new phases

Low-Dimensional Magnetic Semimetal CrAlSe

While exploring novel magnetic semiconductors, the new phase CrAlSe was discovered and characterized by both structural and physical properties. CrAlSe was found to crystallize into orthorhombic CrGeTe-type structure with space group (no. 62). Vacancies and mixed occupancies were tested, and the results show that one of the 4 sites accommodates a mixture of Cr and Al atoms, while the other 4 site is fully occupied by Al atoms. Unique structural features include a T-shaped channel network created from the edge-sharing Cr/Al@Se and Al@Se polyhedra and a zipper effect of the puckered Se atoms inside the columnar channels. The round peak observed in the temperature-dependent magnetic susceptibility (χ) plot at ∼8(1) K corresponds to the antiferromagnetic-type transition in CrAlSe. However, the positive θ indicates an additional ferromagnetic interaction, which is highly likely due to the complex magnetic structure arising from the mixed Cr/Al occupancies on the 4 site. Electrical resistivity measurements confirm that CrAlSe is a semimetal with a positive magnetoresistance. Here we present the characterization and determination of the crystal structure and physical properties for this new material

CrGaSe: A Quasi-Two-Dimensional Magnetic Semiconductor

We present a novel magnetic semiconductor, CrGaSe, synthesized by partially replacing magnetic Cr in antiferromagnetic CrSe with nonmagnetic Ga. The crystal structure of CrGaSe was determined by both powder and single-crystal X-ray diffraction. The title compound crystallizes in a monoclinic structure with space group C2/ m (No. 12). In CrGaSe, the Cr atoms are surrounded by 6 Se atoms and form filled octahedral clusters, while Ga atoms are centered in the Se tetrahedral clusters. The two kinds of clusters pack alternatingly along the c-axis, which results in a quasi-two-dimensional layered structure. The magnetization ( M) measurement shows the development of short-range ferromagnetic coupling below the Curie-Weiss (CW) temperature θ ∼ 92 K, evidenced by the nonlinear field dependence of M. However, the magnetic susceptibility exhibits a peak at low fields at ∼18 K, indicating the existence of an antiferromagnetic interaction as well. Electronic structure calculations using the WIEN2k program in the local spin density approximation indicate that the magnetism arises exclusively from local moments of the Cr atoms. The electrical resistivity measurement of the CrGaSe sample confirms that this material is a semiconductor with the band gap ∼0.26 eV. Meanwhile, the experimental band gap (∼0.26 eV) is close to the theoretical prediction using the WIEN2k program (∼0.35 eV)