Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userHole Doping and Antiferromagnetic Correlations above the N{e}el temperature of the Topological Semimetal (Sr$_{1-x}$K$_x$)MnSb$_2$
57
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Neutron diffraction and magnetic susceptibility studies of orthorhombic single crystal {Ksub} confirm the three dimensional (3D) C-type antiferromagnetic (AFM) ordering of the Mn$^{2+}$ moments at $T_{rm N}=305 pm 3$ K which is slightly higher than that of the parent SrMnSb$_2$ with $T_{rm N}=297 pm 3$ K. Susceptibility measurements of the K-doped and parent crystals above $T_{rm N}$ are characteristic of 2D AFM systems. This is consistent with high temperature neutron diffraction of the parent compound that display persisting 2D AFM correlations well above $T_{rm N}$ to at least $sim 560$ K with no evidence of a ferromagnetic phase. Analysis of the de Haas van Alphen magnetic oscillations of the K-doped crystal is consistent with hole doping.
rate research
Read More
Single crystals of Nd$_2$O$_3$ were grown and characterized using neutron scattering and thermodynamic measurements. Nd$_2$O$_3$ has long-range antiferromagnetic order below $T_{rm N}$ = 0.55 K and specific heat measurements have demonstrated that a significant amount of the magnetic entropy is released above $T_{rm N}$. Inelastic neutron scattering experiments reveal a magnetic mode(s) with little dispersion peaked at $approx$ 0.37 meV that is of greatest intensity below $T_{rm N}$ but persists above 2$T_{rm N}$. This persistence of dynamic correlations is likely related to frustrated interactions associated with the nearly-ideal stacked triangular lattice geometry of $J_{textrm{eff}}$ = 1/2 spins on Nd$^{3+}$ ions. The magnetization is observed to be strongly anisotropic at all temperatures due to crystal field effects, with easy-plane anisotropy observed. A non-compensated magnetic structure is inferred from the temperature-dependence of the magnetization when a magnetic field of sufficient strength is applied within the basal plane near $T_{rm N}$, and the evolution of the long-range order is summarized in a temperature-field phase diagram.
Cd$_3$As$_2$ is one of the prototypical topological Dirac semimetals. Here, we manipulate the band inversion responsible for the emergence of Dirac nodes by alloying Cd$_3$As$_2$ with topologically trivial Zn$_3$As$_2$. We observe the expected topological phase transition around a Zn concentration of $xsim 1$ while the carrier density monotonically decreases as $x$ is increased. For larger $x$, the thermoelectric figure of merit exhibits comparably large values exceeding 0.3 at room temperature, due to the combined effects of a strong enhancement of the thermopower, an only moderate increase of the resistivity, and a suppression of the thermal conductivity. Complementary quantum-oscillation data and optical-conductivity measurements allow to infer that the enhanced thermoelectric performance is due to a flattening of the band structure in the higher-$x$ region in Cd$_{3-x}$Zn$_x$As$_2$.
We investigate the electronic structure of (Sr$_{1-x}$La$_x$)$_2$RhO$_4$ using a combination of the density functional and dynamical mean-field theories. Unlike the earlier local density approximation plus Hubbard $U$ (LDA+U) studies, we find no sizable enhancement of the spin-orbit splitting due to electronic correlations and show that such an enhancement is a spurious effect of the static mean-field approximation of the LDA+U method. The electron doping suppresses the importance of electronic correlations, which is reflected in quasi-particle bandwidth increasing with $x$. (Sr$_{1-x}$La$_x$)$_2$RhO$_4$ can be classified as weakly correlated metal, which becomes an itinerant in-plane ferromagnet (but possibly A-type antiferromagnet) due to Stoner instability around $x=0.2$.
Magnetic topological semimetals have attracted intense attention recently since these materials carry a great promise for potential applications in novel spintronic devices. Here, we report an intimate interplay between lattice, Eu magnetic order and topological semimetallic behavior in Eu$_{1-x}$Sr$_{x}$MnSb$_{2}$ driven by nonmagnetic Sr doping on magnetic Eu site. Different types of Eu spin reorientations are controllable by the Sr concentration, temperature or magnetic field, and coupled to the quantum transport properties of Dirac fermions generated by the 2D Sb layers. Our study opens a new pathway to achieving exotic magnetic order and topological semimetallic state via controlling spin reorientation. The effective strategy of substituting rare-earth site by nonmagnetic element demonstrated here may be applicable to the AMnCh$_{2}$ (A=rare-earth elements; Ch=Bi/Sb) family and a wide variation of other layered compounds involving spatially separated rare-earth and transition metal layers.
We make a new proposal to describe the very low temperature susceptibility of the doped Haldane gap compound Y$_2$BaNi$_{1-x}$Zn$_x$O$_5$. We propose a new mean field model relevant for this compound. The ground state of this mean field model is unconventional because antiferromagnetism coexists with random dimers. We present new susceptibility experiments at very low temperature. We obtain a Curie-Weiss susceptibility $chi(T) sim C / (Theta+T)$ as expected for antiferromagnetic correlations but we do not obtain a direct signature of antiferromagnetic long range order. We explain how to obtain the ``impurity susceptibility $chi_{imp}(T)$ by subtracting the Haldane gap contribution to the total susceptibility. In the temperature range [1 K, 300 K] the experimental data are well fitted by $T chi_{imp}(T) = C_{imp} (1 + T_{imp}/T )^{-gamma}$. In the temperature range [100 mK, 1 K] the experimental data are well fitted by $T chi_{imp}(T) = A ln{(T/T_c)}$, where $T_c$ increases with $x$. This fit suggests the existence of a finite Neel temperature which is however too small to be probed directly in our experiments. We also obtain a maximum in the temperature dependence of the ac-susceptibility $chi(T)$ which suggests the existence of antiferromagnetic correlations at very low temperature.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
