Annealing-Tunable Charge Density Wave in the Magnetic Kagome Material FeGe.

The unprecedented phenomenon that a charge density wave (CDW) emerges inside the antiferromagnetic (AFM) phase indicates an unusual CDW mechanism associated with magnetism in FeGe. Here, we demonstrate that both the CDW and magnetism of FeGe can be effectively tuned through postgrowth annealing treatments. Instead of the short-range CDW reported earlier, a long-range CDW order is realized below 110 K in single crystals annealed at 320 °C for over 48 h. The CDW and AFM transition temperatures appear to be inversely correlated with each other. The onset of the CDW phase significantly reduces the critical field of the spin-flop transition, whereas the CDW transition remains stable against minor variations in magnetic orders such as annealing-induced magnetic clusters and spin-canting transitions. Single-crystal x-ray diffraction measurements reveal substantial disorder on the Ge1 site, which is characterized by displacement of the Ge1 atom from the Fe_{3}Ge layer along the c axis and can be reversibly modified by the annealing process. The observed annealing-tunable CDW and magnetic orders can be well understood in terms of disorder on the Ge1 site. Our study provides a vital starting point for the exploration of the unconventional CDW mechanism in FeGe and of kagome materials in general.

Colossal Zero-Field-Cooled Exchange Bias via Tuning Compensated Ferrimagnetic in Kagome Metals.

Exchange bias (EB) is a crucial property with widespread applications but particularly occurs by complex interfacial magnetic interactions after field cooling. To date, intrinsic zero-field-cooled EB (ZEB) has only emerged in a few bulk frustrated systems and their magnitudes remain small yet. Here, enabled by high temperature synthesis, we uncover a colossal ZEB field of 4.95 kOe via tuning compensated ferrimagnetism in a family of kagome metals, which is almost twice the magnitude of known materials. Atomic-scale structure, spin dynamics, and magnetic theory revealed that these compensated ferrimagnets originate from significant antiferromagnetic exchange interactions embedded in the holmium-iron ferrimagnetic matrix due to supersaturated preferential manganese doping. A random antiferromagnetic order of manganese sublattice sandwiched between ferromagnetic iron kagome bilayers accounts for such unconventional pinning. The outcome of the present study outlines disorder-induced giant bulk ZEB and coercivity in layered frustrated systems.

Vacancies tailoring lattice anharmonicity of Zintl-type thermoelectrics.

While phonon anharmonicity affects lattice thermal conductivity intrinsically and is difficult to be modified, controllable lattice defects routinely function only by scattering phonons extrinsically. Here, through a comprehensive study of crystal structure and lattice dynamics of Zintl-type Sr(Cu,Ag,Zn)Sb thermoelectric compounds using neutron scattering techniques and theoretical simulations, we show that the role of vacancies in suppressing lattice thermal conductivity could extend beyond defect scattering. The vacancies in Sr2ZnSb2 significantly enhance lattice anharmonicity, causing a giant softening and broadening of the entire phonon spectrum and, together with defect scattering, leading to a ~ 86% decrease in the maximum lattice thermal conductivity compared to SrCuSb. We show that this huge lattice change arises from charge density reconstruction, which undermines both interlayer and intralayer atomic bonding strength in the hierarchical structure. These microscopic insights demonstrate a promise of artificially tailoring phonon anharmonicity through lattice defect engineering to manipulate lattice thermal conductivity in the design of energy conversion materials.

Giant magnetocaloric effect in spin supersolid candidate Na2BaCo(PO4)2.

Supersolid, an exotic quantum state of matter that consists of particles forming an incompressible solid structure while simultaneously showing superfluidity of zero viscosity1, is one of the long-standing pursuits in fundamental research2,3. Although the initial report of 4He supersolid turned out to be an artefact4, this intriguing quantum matter has inspired enthusiastic investigations into ultracold quantum gases5-8. Nevertheless, the realization of supersolidity in condensed matter remains elusive. Here we find evidence for a quantum magnetic analogue of supersolid-the spin supersolid-in the recently synthesized triangular-lattice antiferromagnet Na2BaCo(PO4)2 (ref. 9). Notably, a giant magnetocaloric effect related to the spin supersolidity is observed in the demagnetization cooling process, manifesting itself as two prominent valley-like regimes, with the lowest temperature attaining below 100 mK. Not only is there an experimentally determined series of critical fields but the demagnetization cooling profile also shows excellent agreement with the theoretical simulations with an easy-axis Heisenberg model. Neutron diffractions also successfully locate the proposed spin supersolid phases by revealing the coexistence of three-sublattice spin solid order and interlayer incommensurability indicative of the spin superfluidity. Thus, our results reveal a strong entropic effect of the spin supersolid phase in a frustrated quantum magnet and open up a viable and promising avenue for applications in sub-kelvin refrigeration, especially in the context of persistent concerns about helium shortages10,11.

Stability of peri-implantitis surgical reconstructive therapy-a (> 2 years) follow-up of a randomized clinical trial.

OBJECTIVES: This follow-up study aimed to report the 24- and 30-month outcomes of a cohort previously enrolled in a randomized clinical trial on surgical reconstructive treatment of peri-implantitis. METHODS: Twenty-four patients were diagnosed with peri-implantitis and treated with surgical reconstructive therapy with or without the adjunctive use of Er:YAG laser. Within-group and between-group comparisons were tested with mixed model with repeated measures. RESULTS: Regarding peri-implant pocket depth (PPD) reduction (control vs. laser test group) between 6 months (- 1.85 vs. - 2.65 mm) and 30 months (- 1.84 vs. - 3.04 mm), the laser group showed statistically significant changes but not the control group. In terms of radiographic marginal bone loss (RMBL) at 6 months (- 1.1 vs. - 1.46 mm) to 24 months (- 1.96 vs. - 2.82 mm), both groups showed statistical difference compared to baseline. The six explanted implants all were featured by severe peri-implantitis and mostly with no or limited keratinized tissue (< 2 mm) at baseline and membrane exposure after surgery. Among the 15 retained cases, eight cases achieved more than 50% peri-implant bone level gain. CONCLUSIONS: Within the limitation and follow-up time frame of this trial, the outcome of the surgical reconstructive therapy sustained or improved in most of the cases. However, 25% of the implants with severe peri-implantitis failed 2 years after the surgical reconstructive therapy. The use of Er:YAG laser favors PPD reduction in the longer term up to 30 months. CLINICAL RELEVANCE: Longer-term follow-up on reconstructive therapy of peri-implantitis revealed sustained or improved stability in certain cases, but the survival of implants with severe peri-implantitis has its limitation, especially when there is limited keratinized tissue (< 2 mm or no KT). TRIAL REGISTRATION: Clinical Trials Registration Number: NCT03127228 and HUM00160290.