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Jiatu Liu

Publications and source records attributed to Jiatu Liu.

5 recordsLinked to original sources
arXiv2026

Inelastic neutron scattering of the layered Kitaev ferromagnet Li$_3$Co$_2$SbO$_6$

Cobalt-based quantum magnets forming layered honeycomb arrangements have attracted much attention recently, as they are considered as a potential platform for materials with exotic Kitaev spin exchange. Amongst the discussed candidate materials are Na$_3$Co$_2$SbO$_6$ and Na$_2$Co$_2$TeO$_6$, both possessing a low-temperature ground state with some form of antiferromagnetic ordering (zigzag or triple-$Q$), similar to Na$_2$IrO$_3$ and $\alpha$-RuCl$_3$. Here we report inelastic neutron scattering experiments on the quantum magnet Li$_3$Co$_2$SbO$_6$, which features ferromagnetic honeycomb planes with opposite magnetizations in neighboring planes. By comparing with linear spin wave theory, we show that the magnetic properties of Li$_3$Co$_2$SbO$_6$ can be well-modelled by an extended Kitaev--Heisenberg model, establishing it as a Kitaev-ferromagnet, or more specifically, as a Kitaev A-type antiferromagnet. Our analysis is complemented by magnetic field measurements and simulations.

cond-mat.str-el↗
arXiv2023

Robust room temperature ferromagnetism in an itinerant van der Waals antiferromagnet

The coexistence of antiferromagnetic and ferromagnetic order at room temperature in single-phase van der Waals materials, particularly within the two-dimensional limit, has attracted significant research interest. Nonetheless, such materials are rare. In this work, we introduce an itinerant van der Waals antiferromagnet (Fe0.56Co0.44)5GeTe2, where the ferromagnetic order of its exfoliated flakes remains discernible up to room temperature, extending down to the monolayer limit. A notable phenomenon observed is the evident odd-even layer-number effect at high temperature (e.g., T = 150 K). Such behaviour can be expounded by a linear-chain model. Of particular interest is the robust ferromagnetic order observed in even-layer flakes at low temperature (e.g., T = 2 K), which could potentially be attributed to spin-polarized defects. The intricate interplay among magnetic field strength, layer number, and temperature gives rise to a diverse array of phenomena, holding promise not only for new physics but also for practical applications.

cond-mat.str-el↗
arXiv2022

Dominant Kitaev interactions in the honeycomb materials Na$_3$Co$_2$SbO$_6$ and Na$_2$Co$_2$TeO$_6$

Cobaltates with 3$d$ based layered honeycomb structure were recently proposed as Kitaev magnets and putative candidates to host the long-sought Kitaev spin liquid. Here we present inelastic neutron scattering results down to 50 mK for powder samples of Na$_3$Co$_2$SbO$_6$ and Na$_2$Co$_2$TeO$_6$, with high resolution in regions of low momentum and energy transfers. We compare the experimental data below the antiferromagnetic zigzag ordering temperature with dynamical structure factors obtained within spin wave theory. We search the wide parameter range of a $K$-$J_1$-$Γ$-$Γ^{\prime}$-$J_3$ spin 1/2 model and identify the best fits to constant momentum cuts of the inelastic neutron data. The powder average limits the selection of a unique parameter set for each material, but we see clear trends towards ferromagnetic Kitaev exchange in both compounds, and ratios $|K/J_1|$ could be as large as $5\ldots 25$; in contrast, antiferromagnetic Kitaev exchange cannot be ruled out, but requires a fine-tuning of all involved spin exchange couplings with only moderate ratio $|K/J_1| \sim 1$. Our experimental data are incompatible with a purely isotropic Heisenberg model.

cond-mat.str-el↗
arXiv2022

Structural and phase evolution in U$_3$Si$_2$ during steam corrosion

U$_3$Si$_2$ nuclear fuel is corroded in deuterated steam with in situ neutron diffraction. Density functional theory is coupled with rigorous thermodynamic description of the hydride including gas/solid entropy contributions. H absorbs in the 2$b$ interstitial site of U$_3$Si$_2$H$_x$ and moves to 8$j$ for $x\ge 0.5$. Hydriding forces lattice expansion and change in $a/c$ ratio linked to site preference. Rietveld refinement tracks the corrosion reactions at 350-500 °C and preference for the 8j site. Above 375 °C, formation of UO$_2$, U$_3$Si$_5$ and USi$_3$ take place in the grain boundaries and bulk. Hydriding occurs in bulk and precedes other reactions.

cond-mat.mtrl-sci↗