Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMagnetic order in the chemically-substituted frustrated antiferromagnet CsCrF$_{4}$
104
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The effect of chemical substitution on the ground state of the geometrically frustrated antiferromagnet CsCrF$_4$ has been investigated through a neutron powder diffraction experiment. Magnetic Fe-substituted CsCr$_{0.94}$Fe$_{0.06}$F$_{4}$ and nonmagnetic Al-substituted CsCr$_{0.98}$Al$_{0.02}$F$_{4}$ samples are measured, and magnetic Bragg peaks are clearly observed in both samples. Magnetic structure analysis revealed a 120$^{circ}$ structure having a magnetic propagation vector $mathbf{k}_{rm mag}=(0,0,1/2)$ in CsCr$_{0.94}$Fe$_{0.06}$F$_{4}$. For CsCr$_{0.98}$Al$_{0.02}$F$_{4}$, a quasi-120$^{circ}$ structure having $mathbf{k}_{rm mag}=(1/2,0,1/2)$ is formed. It is notable that the identified magnetic structure in CsCr$_{0.94}$Fe$_{0.06}$F$_{4}$ belongs to a different phase of ground states from those in CsCr$_{0.98}$Al$_{0.02}$F$_{4}$ and the parent CsCrF$_{4}$. These results suggest that the Fe-substitution strongly influences the ground state of CsCrF$_{4}$.
rate research
Read More
The frustrated pyrochlore antiferromagnet Gd$_{2}$Ti$_{2}$O$_{7}$ has an unusual partially-ordered magnetic structure at the lowest measurable temperatures. This structure is currently believed to involve four magnetic propagation vectors $mathbf{k}in langle frac{1}{2} frac{1}{2} frac{1}{2} rangle^*$ in a cubic 4-$mathbf{k}$ structure, based on analysis of magnetic diffuse-scattering data [J. Phys.: Condens. Matter 16, L321 (2004)]. Here, we present three pieces of evidence against the 4-$mathbf{k}$ structure. First, we report single-crystal neutron-diffraction measurements as a function of applied magnetic field, which are consistent with the selective field-induced population of non-cubic magnetic domains. Second, we present evidence from high-resolution powder neutron-diffraction measurements that rhombohedral strains exist within magnetic domains, which may be generated by magneto-elastic coupling only for the alternative 1-$mathbf{k}$ structure. Finally, we show that the argument previously used to rule out the 1-$mathbf{k}$ structure is flawed, and demonstrate that magnetic diffuse-scattering data can actually be fitted quantitatively by a 1-$mathbf{k}$ structure in which spin fluctuations on ordered and disordered magnetic sites are strongly coupled. Our results provide an experimental foundation on which to base theoretical descriptions of partially-ordered states.
Partially-ordered magnets are distinct from both spin liquids and conventional ordered magnets because order and disorder coexist in the same magnetic phase. Here, we determine the nature of partial order in the canonical frustrated pyrochlore antiferromagnet Gd$_2$Ti$_{2}$O$_{7}$. Using single-crystal neutron-diffraction measurements in applied magnetic field, magnetic symmetry analysis, inelastic neutron-scattering measurements, and spin-wave modeling, we show that its low-temperature magnetic structure involves two propagation vectors (2-$mathbf{k}$ structure) with suppressed ordered magnetic moments and enhanced spin-wave fluctuations. Our experimental results support theoretical predictions of thermal fluctuation-driven order in Gd$_{2}$Ti$_{2}$O$_{7}$.
We report a high-resolution neutron diffraction study of the crystal and magnetic structure of the orbitally-degenerate frustrated metallic magnet AgNiO2. At high temperatures the structure is hexagonal with a single crystallographic Ni site, low-spin Ni3+ with spin-1/2 and two-fold orbital degeneracy, arranged in an antiferromagnetic triangular lattice with frustrated spin and orbital order. A structural transition occurs upon cooling below 365 K to a tripled hexagonal unit cell containing three crystallographically-distinct Ni sites with expanded and contracted NiO6 octahedra, naturally explained by spontaneous charge order on the Ni triangular layers. No Jahn-Teller distortions occur, suggesting that charge order occurs in order to lift the orbital degeneracy. Symmetry analysis of the inferred Ni charge order pattern and the observed oxygen displacement pattern suggests that the transition could be mediated by charge fluctuations at the Ni sites coupled to a soft oxygen optical phonon breathing mode. At low temperatures the electron-rich Ni sublattice (assigned to a valence close to Ni2+ with S = 1) orders magnetically into a collinear stripe structure of ferromagnetic rows ordered antiferromagnetically in the triangular planes. We discuss the stability of this uncommon spin order pattern in the context of an easy-axis triangular antiferromagnet with additional weak second neighbor interactions and interlayer couplings.
By means of high-resolution ultrasonic velocity measurements, as a function of temperature and magnetic field, the nature of the different low temperatures magnetic phase transitions observed for the quasi-one-dimensional compound CsNiCl3 is established. Special attention has been devoted to the field-induced 120 degree phase transition above the multicritical point in the H-T phase diagram where the elastic constant C44 reveals a step-like variation and hysteresis effects. These results represent the first experimental evidence that the 120 degree phase transition is weakly first order and contradict the popular notion of new universality classes for chiral systems.
Barlowite, Cu$_{4}$(OH)$_{6}$FBr, has attracted much attention as the parent compound of a new series of quantum spin liquid candidates, Zn$_{x}$Cu$_{4-x}$(OH)$_{6}$FBr. While it is known to undergo a magnetic phase transition to a long-range ordered state at $T_{N} = 15$ K, there is still no consensus over either its nuclear or magnetic structures. Here, we use comprehensive powder neutron diffraction studies on deuterated samples of barlowite to demonstrate that the only space group consistent with the observed nuclear and magnetic diffraction at low-temperatures is the orthorhombic $Pnma$ space group. We furthermore conclude that the magnetic intensity at $T < T_{N}$ is correctly described by the $Pn^prime m^prime a$ magnetic space group, which crucially allows the ferromagnetic component observed in previous single-crystal and powder magnetisation measurements. As such, the magnetic structure of barlowite resembles that of the related material clinoatacamite, Cu$_{4}$(OH)$_{6}$Cl$_{2}$, the parent compound of the well-known quantum spin liquid candidate hebertsmithite, ZnCu$_{3}$(OH)$_{6}$Cl$_{2}$.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
