Three-dimensionally (3D) frustrated magnets generally exist in the magnetic diamond and pyrochlore lattices, in which quantum fluctuations suppress magnetic orders and generate highly entangled ground states. LiYbSe 2 in a previously unreported pyrochlore lattice was discovered from LiCl flux growth. Distinct from the quantum spin liquid (QSL) candidate NaYbSe 2 hosting a perfect triangular lattice of Yb 3+ , LiYbSe 2 crystallizes in the cubic pyrochlore structure with space group Fd3m (No. 227). The Yb 3+ ions in LiYbSe 2 are arranged on a network of corner-sharing tetrahedra, which is particularly susceptible to geometrical frustration. According to our temperature-dependent magnetic susceptibility measurements, the dominant antiferromagnetic interaction in LiYbSe 2 is expected to appear around 8 K. However, no long-range magnetic order is detected in thermomagnetic measurements above 70 mK. Specific heat measurements also show magnetic correlations shifting with applied magnetic field with a degree of missing entropy that may be related to the slight mixture of Yb 3+ on the Li site. Such magnetic frustration of Yb 3+ is rare in pyrochlore structures. Thus, LiYbSe 2 shows promise in intrinsically realizing disordered quantum states like QSL in pyrochlore structures.
The new Eu 5 Al 3 Sb 6 phase has been successfully synthesized as a pure phase through Sn flux methods yielding large, high-quality crystals. This structure type features disordered Al clusters that appear in the form of dual tetrahedra. It crystallizes in the monoclinic C2/m space group exhibiting a rock-salt-like Eu−Sb framework with [Al 4 ] tetrahedra replacing some of the cationic Eu atoms (space group: C2/m, a = 8.151(1) Å, b = 14.181(2) Å, c = 8.145(1) Å, β = 109.577(2)°). The structure models the [Al 4 ] as dual tetrahedra with the Al atom sites 37.5% occupied along with Eu present on the central site at 8% occupancy and the remainder of the site being vacant. The presence of the [Al 4 ] cluster is further supported by HRTEM. Electronic structure calculations show that this material is a semimetal with observed band crossings close to the Fermi level. Strong Al−Sb antibonding interactions were found from COHP calculations close to the Fermi level and provide the rationale for the deficiency of the Al cluster. Mossbauer spectroscopy on Eu-151 and Sb-121 provides oxidation states of 2+ and 3− along with the local environment. Magnetic susceptibility measurements can be described well with a Curie−Weiss law where an effective moment of 7.80 μ B /mol Eu is obtained, consistent with Eu 2+ , and show canted antiferromagnetic behavior below 10 K. Temperature dependent resistivity shows a Kondo-like low-temperature upturn caused by enhanced scattering of the itinerant electrons with the 4f orbitals of Eu.
A series of garnets of formula Er3+x Ga5–x O12 are described, for which we report the crystal structures for both polycrystalline and single-crystal samples. The x limit in the garnet phase is between 0.5 and 0.6 under our conditions, with the Er fully occupying the dodecahedral (24c) garnet site plus some of the octahedral site (16a) in place of the Ga normally present. Long-range antiferromagnetic order with spin-ice-like frustration is suggested by the transition temperature (T N ≈ 0.8 K) being lower than the Curie–Weiss theta. The magnetic ordering temperature does not depend on the Er excess, but there is increasing residual entropy as the Er excess is increased, highlighting the potential for unusual magnetic behavior in this system. The field-dependent magnetic entropy trend is consistent with the reported behavior for frustrated triangular magnetic systems: an increasing transition temperature with a broader hump as the applied field increases [XingJ. Xing, J. 114413Phys. Rev. Mater.20193 FilippiJ. Filippi, J. Solid State Commun.197723613616; Thermal and Magnetic Studies of Spin Ice CompoundsBloxsomJ. A. Bloxsom, J. A. University College London2016.
Magnetic structure and crystal symmetry, which primarily determine the time-reversal and inversion symmetry, may give rise to numerous exotic quantum phenomena in magnetic semiconductors and semimetals when arranged in different patterns. In this work, a new layered magnetic semiconductor, Eu3−δZn xSn yAs3, was discovered and high-quality single crystals were grown using the Sn flux. According to structural characterization by x-ray diffraction and atomic-resolution scanning transmission electron microscopy, Eu3−δZn xSn yAs3 is found to crystallize in a hexagonal symmetry with the space group P63/ mmc (No. 194). After examining different specimens, we conclude that their stoichiometry is fixed at ∼Eu2.6Zn0.65Sn0.85As3, which meets the chemical charge balance. Eu3−δZn xSn yAs3 is composed of septuple (Eu1−δSn yAs2)-Eu-(Zn xAs)-Eu sequences. The shortest Eu–Eu distance in the system is between two Eu layers separated by Zn xAs along the c-axis. Magnetization measurement shows an antiferromagnetic ordering in Eu3−δZn xSn yAs3 at TN ∼ 12 K, where the magnetic easy-axis is along the c-axis, and Mössbauer spectroscopy observes magnetic hyperfine splitting on Eu and Sn at 6 K. Magnetic anisotropy is significantly different from the ones along the ab-plane in other layered Eu-based magnetic semimetals. Heat capacity measurements confirm the magnetic transition around 12 K. Electrical resistivity measurement indicates semiconductor behavior with a band gap of ∼0.86 eV. Various Eu-based magnetic semiconductors could provide a tunable platform to study potential topological and magnetic properties.
The previously unreported layered compounds IrTe2I and RhTe2I were prepared by a high-pressure synthesis method. Single crystal X-ray and powder X-ray diffraction studies find that the compounds are isostructural, crystallizing...
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