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Yb-site deficiency and sample-dependent thermal and magnetic hysteresis in kagome antiferromagnet YbMn6Ge6

Wed, 30 Sep 2026 15:00:00 GMT

Title: Yb-site deficiency and sample-dependent thermal and magnetic hysteresis in kagome antiferromagnet YbMn6Ge6 Author(s): Park, Jaemun; Choi, Woo-Jae; 이태성; Baek, Wonjung; Cho, Beopgil; Kwon, Yong-Seung; Choi, Yojong; Song, Seunghyun; Kim, Myung-Su; Choi, Yeon Suk; Park, Keeseong Abstract: YbMn6Ge6 is an antiferromagnet in which Yb3+ moments couple to the kagome Mn sublattice, stabilizing a conical incommensurate magnetic state at low temperature. However, previously reported magnetization and resistivity behaviors remain partially inconsistent. Here, we demonstrate pronounced sample-dependent thermal and magnetic hysteresis in YbMn6Ge6 single crystals grown by the Sn-flux method and show that these variations are consistent with Yb-site deficiency and possible spatial inhomogeneity. Both structural and chemical composition analyses indicate Yb vacancies in all crystals. The transition onset temperature and its width vary between batches with different inferred Yb occupancies: in resistivity measurements, crystals with higher Yb occupancy exhibit transitions at 68 K (cooling) and 80 K (heating), whereas samples with lower inferred Yb occupancy display a broadened transition window of 110-128 K. While these transitions are also reflected in magnetization measurements, measurements on crystals and smaller fragments suggest that the apparent onset is governed not simply by macroscopic sample size but also by a distribution of local transition temperatures. Weak and sample-dependent signatures, including the presence of thermal hysteresis, are also found in specific heat measurements, indicating that spatial averaging over inhomogeneous regions can smear thermodynamic signatures. At low temperature, we further observe strongly anisotropic field-induced metamagnetic hysteresis and its sensitivity to the sample-dependent defect landscape. Magnetoresistance measurements track the metamagnetic features, indicating a close correlation between magnetic order and charge transport. Overall, our results suggest that Yb-site deficiency and associated spatial inhomogeneity are important factors governing the sample-dependent hysteretic behavior and highlight the importance of the R-site chemistry in the isostructural RMn6Ge6 family.

Electronic structure of the thermoelectric charge density wave material CeTe2-xSbx investigated via angle-resolved photoemission spectroscopy

Tue, 30 Jun 2026 15:00:00 GMT

Title: Electronic structure of the thermoelectric charge density wave material CeTe2-xSbx investigated via angle-resolved photoemission spectroscopy Author(s): Seong, Seungho; Han, Sang Wook; Min, B. I.; Kwon, Yong Seung; Kang, J. -S Abstract: Employing angle-resolved photoemission spectroscopy (ARPES), we have investigated the electronic structures of Sb-substituted CeTe2, CeTe2-xSbx(0 <= x <= 0.5), which exhibit charge density wave (CDW) transitions and enhanced thermoelectric (TE) properties and are also predicted to be topological material candidates. Two flat Ce 4 f states are observed, one at approximately-3.5 eV and the other at approximately-0.8 eV, which represent the 4 f (1)-> 4 f(0 )transition and the Kondo-like 4 f(1) L-0 -> 4 f(1) L(1 )transition (where L & strns; is a ligand hole) of trivalent Ce3+ ions, respectively. Two diamond-shaped inner and outer Fermi surfaces (FSs) are observed, which arise from the holelike band centered at P and from the folding of the two-dimensional Brillouin zone (BZ) into the three-dimensional (3D) BZ, respectively. The measured outer FSs demonstrate the non-negligible effect of the 3D electronic structures of CeTe2-xSbx. The CDW-induced zigzag features are observed in the FS of x = 0, but are not observed in the FSs of x > 0, indicating the rapid suppression of the CDW state by the Sb substitution. This finding suggests that the increased resistivity at x > 0, despite the weakened CDW formation, is possibly due to the disorder-induced localization by the Sb substitution, leading to the optimal TE properties at a specific x. The measured band structures of CeTe(2-x)Sb(x)via ARPES exhibit very similar features for different x values, except for the shift of the whole bands toward the Fermi level (EF) with increasing x. This reflects the hole doping introduced by the Sb substitution, which is in good agreement with the calculated band structures. In the ARPES data of x > 0, crossing bands are observed near the X point at approximately-1 eV, which closely resemble Dirac points, suggesting the existence of topological electronic structures of CeTe2-xSbx. Linear dichroism ARPES measurements on CeTe1.75Sb0.25 show that the EF-crossing Te/Sb p states along X-P-X and M-P-M have both in-plane and out-of-plane character, while those along M-X-M have mainly in-plane character.

A comparative synthesis study of α-MnTe across solid-state, Arc-melting, and Te-flux routes

Fri, 31 Jul 2026 15:00:00 GMT

Title: A comparative synthesis study of α-MnTe across solid-state, Arc-melting, and Te-flux routes Author(s): Kim, Bomin; Jeong, Yunseong; Baek, Wonjung; Kim, Hobyeong; 이태성; Cho, Beopgil; Choi, Woojae; Ha, Jae-Hyun; Park, Jaemun; Hong, Jung-Il; Kwon, Yong Seung; Seo, Jungpil; Park, Keeseong Abstract: Although alpha-MnTe has attracted renewed interest in both thermoelectric and altermagnetic contexts, direct comparisons of practically accessible synthesis routes within a common experimental framework remain limited. Here, we compare conventional solid-state reaction, arc melting and Te self-flux growth methods under a common framework of composition control and thermal history. Within the explored conditions, the phase outcome depends not only on the nominal starting composition but also on route-dependent synthesis environments, including volatilization in sealed ampoules, repeated remelting and rapid quenching in arc melting, and crystal-flux interfacial segregation in Te self-flux growth. In the solid-state route, slow heating with a slightly Mn-rich starting composition was associated with reduced MnTe2 and alpha-MnTe-dominant products. Arc melting yielded alpha-MnTe-dominant products without post-annealing, accompanied by dendritic-like microstructures. Te self-flux growth yielded single crystals, although a minor MnTe2-rich interfacial or surface layer often remained. While the present dataset does not define a rigorous phase boundary or a definitive mechanistic model, it provides a systematic comparative framework for route-dependent phase outcomes and impurity persistence in alpha-MnTe synthesis.

A comparative synthesis study of α-MnTe across solid-state, Arc-melting, and Te-flux routes

Fri, 31 Jul 2026 15:00:00 GMT