Antiferromagnetic resonance in NaCrS2

Antiferromagnetic resonance measurements in rhombohedral NaCrS₂ (T_N = 17 K) are reported. The data are compared with theory developed by Battles for a collinear easy-plane antiferromagnet with anisotropy in the basal plane. While there is reasonable agreement with this theory, some discrepancies occur. These are presumably related to low-temperature in-plane distortions from hexagonal symmetry, previously postulated by other workers.     

Antiferromagnetic metallic state of NiS2

The neutron diffraction experiment we have made on NiS_1.91 single crystal under increasing pressure (0<P<30 kbar) indicates a constant increase of the Néel temperature of the sample. For high pressures (P>20 kbar) and low temperatures the sample is in an antiferromagnetic metallic state as suggested by theoretical considerations for a Mott-Hubbard insulator. The pressure dependence of the second magnetic transition in NiS₂ (T = 31 K for P = 0) is also reported.     

Second-Harmonic Response in Magnetic Nodal-Line Semimetal Fe3GeTe2

We experimentally investigate second-harmonic transverse voltage response to ac electrical current for a magnetic nodal-line semimetal Fe₃GeTe₂(FGT). For zero magnetic field, the observed second-harmonic voltage behaves as a square of the longitudinal current, as it should be expected for nonlinear Hall effect. The magnetic field behavior is found to be sophisticated: while the first-harmonic response shows the known anomalous Hall hysteresis in FGT, the second-harmonic Hal...     

Antiferromagnetic resonance in α-RbMnCl3 · 2H2O

Antiferromagnetic resonance results on α-RbMnCl₃ · 2H₂O below the Néel temperature 4.56 K are reported. At T = 1.2K we find for the anisotropy fields H^c = 440 Oe and H^a = 1510 Oe. The spin flop field at T = 1.2K is 14.62 kOe.     

Antiferromagnetic resonance of (C2H5NH3)2CuCl4

Antiferromagnetic resonance of (C₂H₅NH₃)₂CuCl₄ was studied at 1 GHz region. Characteristics of a weak exchange interaction with a strong anisotropy were observed.     

Antiferromagnetic versus spin-glass like behavior in MnIn2S4

The low-temperature magnetic properties of MnIn₂S₄ have been studied using AC magnetic susceptibility and magnetization experiments. High-temperature susceptibility fits indicate the presence of antiferromagnetic interactions. Low-field magnetization data show a peak at 5.6±0.1 K, below which strong irreversibility is observed between zero-field-cooled (ZFC) and field-cooled (FC) cycles suggesting that the observed peak corresponds to a spin-glass-like transition instead of the antiferromagnetic one previously reported. Further evidence of this magnetic state comes from AC susceptibility data at different frequencies. The in-phase component χ′(T) exhibits the behavior expected of spin glasses, i.e. a shift of the cusp to higher temperatures for higher frequencies.     

Electronic Structure of the Weak Topological Insulator Candidate Zintl Ba3Cd2Sb4

One of the greatest triumph of condensed matter physics in the past ten years is the classification of materials by the principle of topology.The existence of topological protected dissipationless surface state makes topological insulators great potential for applications and hotly studied.However,compared with the prosperity of strong topological insulators,theoretical predicted candidate materials and experimental confirmation of weak topological insulators(WTIs) are both extremely rare.By com...     

Topological Nodal Line Semimetal in Non-Centrosymmetric PbTaS_2

Topological semimetals are a new type of matter with one-dimensional Fermi lines or zero-dimensional Weyl or Dirac points in momentum space. Here using first-principles calculations, we find that the non-centrosymmetric PbTaS2 is a topological nodal line semimetal. In the absence of spin-orbit coupling(SOC), one band inversion happens around a high symmetrical H point, which leads to forming a nodal line. The nodal line is robust and protected against gap opening by mirror reflection symmetry even with the inclusion of strong SOC. In addition, it also hosts exotic drumhead surface states either inside or outside the projected nodal ring depending on surface termination. The robust bulk nodal lines and drumhead-like surface states with SOC in PbTaS_2 make it a potential candidate material for exploring the freakish properties of the topological nodal line fermions in condensed matter systems.     

Antiferromagnetic order and spin glass behavior in Dy2CuIn3

The magnetic properties of the intermetallic compound Dy₂CuIn₃ have been investigated. Ac and dc-susceptibility measurements indicate an onset of antiferromagnetic ordering at T_N=19.5 K and an additional frequency dependent transition at T_ds∼9 K. Neutron diffraction studies confirm the ordered transition at 19.5±1 K. The magnetic unit cell can be described by the propagation vector k=(0.25,0.25,0) with the magnetic moment μ=2.63(4)μ_B/Dy³⁺ parallel to the c-axis. Nevertheless, neutron diffraction reveals no additional magnetic phase transition around or below 9 K, which suggests that, at lower temperatures, a spin glass state may be formed in coexistence with the antiferromagnetic mode as a result of frustration and the antagonism between ferromagnetic and antiferromagnetic exchange interactions.     

Antiferromagnetic phase transition in garnet-type AgCa2Co2V3O12 and AgCa2Ni2V3O12

Antiferromagnetic phase transition in two vanadium garnets AgCa₂Co₂V₃O₁₂ and AgCa₂Ni₂V₃O₁₂ has been found and investigated extensively. The heat capacity exhibits sharp peak due to the antiferromagnetic order with the Néel temperature T_N=6.39 K for AgCa₂Co₂V₃O₁₂ and 7.21 K for AgCa₂Ni₂V₃O₁₂, respectively. The magnetic susceptibilities exhibit broad maximum, and these T_N correspond to the inflection points of the magnetic susceptibility χ a little lower than T(χ_max). The magnetic entropy changes from zero to 20 K per mol Co²⁺ and Ni²⁺ ions are 5.31 J K⁻¹ mol-Co²⁺-ion⁻¹ and 6.85 J K⁻¹ mol-Ni²⁺-ion⁻¹, indicating S=1/2 for Co²⁺ ion and S=1 for Ni²⁺ ion. The magnetic susceptibility of AgCa₂Ni₂V₃O₁₂ shows the Curie-Weiss behavior between 20 and 350 K with the effective magnetic moment μ_eff=3.23 μ_B Ni²⁺-ion⁻¹ and the Weiss constant θ=−16.4 K (antiferromagnetic sign). Nevertheless, the simple Curie-Weiss law cannot be applicable for AgCa₂Co₂V₃O₁₂. The complex temperature dependence of magnetic susceptibility has been interpreted within the framework of Tanabe-Sugano energy diagram, which is analyzed on the basis of crystalline electric field. The ground state is the spin doublet state ²E(t₂⁶e) and the first excited state is spin quartet state ⁴T₁(t₂⁵e²) which locates extremely close to the ground state. The low spin state S=1/2 for Co²⁺ ion is verified experimentally at least below 20 K which is in agreement with the result of the heat capacity.     

Antiferromagnetic Heisenberg S=5/2 spin chain compound SrMn2V2O8

Large single crystals of the new compound SrMn₂V₂O₈ have been grown by the floating-zone method. This transition-metal based oxide is isostructural to SrNi₂V₂O₈, described by the tetragonal space group I4₁cd. Magnetic properties were investigated by means of susceptibility, magnetization, and specific-heat measurements. The compound behaves like a 1D magnetic system above the ordering temperature (T_N=43 K). The magnetic ground state can be described as a classical long-range ordered antiferromagnet with weak anisotropy.     

Antiferromagnetic transition in botallackite Cu2Cl(OH)3

The natural cuprate botallackite, Cu₂Cl(OH)₃, is found to be a new antiferromagnet with Magnetic susceptibility properties under strong field show non-linear M-H properties indicating metamagnetism. The T_N and the super-exchange coupling are discussed and compared with its polymorph atacamite and other copper oxides on the basis of their structural parameters.     

Antiferromagnetic resonance in ferroborate NdFe3(BO3)4

The AFMR spectra of the NdFe₃(BO₃)₄ crystal are measured in a wide range of frequencies and temperatures. It is found that by the type of its magnetic anisotropy the compound is an “easy-plane” antiferromagnet with a weak anisotropy in the basal plane. The effective magnetic parameters are determined: anisotropy fields H_a1=1.14 kOe and H_a2=60 kOe and magnetic excitation gaps Δν₁=101.9 GHz and Δν₂=23.8 GHz. It is shown that commensurate-incommensurate phase transition causes a shift in resonance field and a considerable change in absorption line width.At temperatures below 4.2 K nonlinear regimes of AFMR excitation at low microwave power levels are observed.     

Antiferromagnetic Mn50Fe50 wire with large magnetostriction

This work presents a study on the relation between the fiber texture and the magnetostrictive performance in an antiferromagnetic Mn₅₀Fe₅₀ alloy wire, which was prepared through the combining process of hot rolling and cold drawing. The face-centered cubic (fcc) crystal structure can be retained during the plastic deformation process. Mixed fiber textures consisting of both 1 1 0 and 1 0 0 components were formed along the drawing direction (DD) in the wire. A large magnetostriction of 750 ppm was obtained along DD under 1.2 T, which can be ascribed to the single γ phase and the formation of preferred crystal orientation.     

A Complete Frequency-Field Chart for the Antiferromagnetic Resonance in MnF2

Antiferromagnetic resonance (AFMR) measurements on a well characterized single crystal sample of MnF₂ have been performed using various kinds of millimeter and submillimeter sources up to 570 GHz and a superconducting magnet up to 20 T. All the AFMR modes predicted from the theory have been observed. We report a complete frequency-field chart for these AFMR modes.     

Quantum Oscillations and Electronic Structure in the Large-Chern-Number Topological Chiral Semimetal PtGa

We report the magnetoresistance(MR),de Haas-van Alphen(dHvA) oscillations and the electronic structures of single-crystal PtGa.The large unsaturated MR is observed with the magnetic field B ‖ [111].Evident dHvA oscillations with the B ‖ [001] configuration are observed,from which twelve fundamental frequencies are extracted and the spin-orbit coupling(SOC) induced band splitting is revealed.The light cyclotron effective masses are extracted from the fitting by the thermal damping term of the Lif...     

Negative Magnetoresistance in Antiferromagnetic Topological Insulator EuSn_2As_2

The measurements of magnetization,longitudinal and Hall resistivities are carried out on the intrinsic antiferromagnetic(AFM) topological insulator ElSn_2 As_2.It is confirmed that our ElSn_2 As_2 crystal is a heavily hole doping A-type AFM metal with the Neel temperature T_N=24 K,with a metamagnetic transition from an AFM to a ferromagnetic(FIM) phase occurring at a certain critical magnetic Held for the different Held orientations.Meanwhile,we also find that the carrier concentration does not change with the evolution of magnetic order,indicating that the weak interaction between the localized magnetic moments from Eu~(2+)4f~7 orbits and the electronic states near the Fermi level.Although the quantum anomalous Hall effect(AHE) is not observed in our crystals,it is found that a relatively large negative magnetoresistance (-13%) emerges in the AFM phase,and exhibits an exponential dependence upon magnetic Held,whose microscopic origin is waiting to be clarified in future research.     

压力对纳米CoFe2O4/SiO2复合材料结构的影响

 采用溶胶-凝胶工艺和高温高压实验技术,制备了纳米CoFe₂O₄/SiO₂复合材料。利用X射线衍射仪、扫描电子显微镜和振动样品磁强计,对样品的结构、微观形貌和磁性进行了研究,并对CoFe₂O₄中阳离子的占位情况进行了讨论。结果表明,随着处理压力的升高,样品的晶粒尺寸增大,晶格常数减小,比饱和磁化强度增大。通过计算结果可以推断,压力的升高导致CoFe₂O₄中的部分Fe³⁺从A位移向了B位,而部分Co²⁺则从B位移向了A位。     

Structure and elastic properties of TeO2-BaF2 glasses

Binary tellurite (100−x)TeO₂-xBaF₂ glasses for different compositions of BaF₂ (x=8, 10, 12, 15, 18 and 20 wt%) have been prepared by rapid quenching method. The velocities and attenuation during the propagation of the ultrasonic waves in all glasses were measured using a transducer operated at a fundamental frequency of 5 MHz at room temperature. A progressive increase in BaF₂ content leads to a decrease in ultrasonic velocities and density, which is followed by an increase in attenuation. The existence of depolymerisation of Te co-ordination leads to the transformation of TeO₄ trigonal bipyramid units through TeO₃₊₁ polyhedron to TeO₃ trigonal pyramid units. This is responsible for the observed decrease in the measured and determined parameters with the addition of the modifier content.