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Abstract Kagome materials are of topical interest for their diverse quantum properties linked with correlated magnetism and topology. Here, we report anomalous hydrostatic pressure (p) effect on ErMn6Sn6 through isobaric and isothermal-isobaric magnetization measurements. Magnetic field (H) suppresses antiferromagnetic T N while simultaneously enhancing the ferrimagnetic T C by exhibiting dual metamagnetic transitions, arising from the triple-spiral-nature of Er and Mn spins. Counter-intuitively, pressure enhances both T C and T N with a growth rate of 74.4 K GPa−1 and 14.4 K GPa−1 respectively. Pressure unifies the dual metamagnetic transitions as illustrated through p-H phase diagrams at 140 and 200 K. Temperature-field-pressure (T-H, T-p) phase diagrams illustrate distinct field- and pressure-induced critical points at (T cr = 246 K, H cr = 23.3 kOe) and (T cr = 435.8 K, p cr = 4.74 GPa) respectively. An unusual increase of magnetic entropy by pressure around T cr and a putative pressure-induced tricritical point pave a unique way of tuning the magnetic properties of kagome magnets through simultaneous application of H and p.

Abstract The interaction between multi‐component rare earth element (REE) aqueous solutions and carbonate grains (dolomite, aragonite, and calcite) are studied at hydrothermal conditions (21–210 °C). The effect of ionic radii of five REEs (La, Ce, Pr, Nd, Dy) on solid formation are analyzed using two solution types: equal REE concentrations and concentrations normalized to Post Archean Australian Shale Standard (PAAS). The interaction replaces the host Ca–Mg carbonate grains with a series of REE minerals (lanthanite → kozoite → bastnäsite → cerianite). At 165 °C, equal concentration solutions promote kozoite crystallization, maintaining similar REE ratios in solids and solution. PAAS solutions result in zoned REE‐bearing crystals with heterogeneous elemental distributions and discreet REE phases (e.g., cerianite). Chemical signatures indicate metastable REE‐bearing phases transforming into more stable polymorphs, along with symplectite textures formed by adjacent phase reactions. Overall, experiments highlight the dependence of polymorph selection, crystallization pathway, mineral formation kinetics, and chemical texture on REE concentrations, ionic radii, temperature, time, and host grain solubility.

Abstract The interaction between rare earth element (REE)‐rich (La, Pr, Nd, Dy) aqueous solutions, dolomite (CaMg(CO3)2), and aragonite (CaCO3) at low temperature hydrothermal conditions (25–220 °C) is studied. The experiments result in the solvent‐mediated surface precipitation and subsequent pseudomorphic mineral replacement of the dolomite and aragonite seeds by newly formed REE‐carbonates. The host grains are replaced from periphery inward. The newly formed REE‐bearing carbonates in La‐, Pr‐, and Nd‐doped systems follow the crystallization sequence: lanthanite [REE2(CO3)3·8H2O] → kozoite [orthorhombic REECO3(OH)] → hydroxylbastnasite [hexagonal REECO3(OH)]. The interaction of Dy‐bearing solutions with dolomite results only in the crystallization of kozoite [orthorhombic DyCO3(OH)]. However, experiments with aragonite reveal a two‐step crystallization pathway: tengerite [Dy2(CO3)3·2‐3(H2O)] → kozoite [orthorhombic DyCO3(OH)]. The temperature, the dissolution rate of the host mineral, and the ionic radii of the REE3+ in question are found to control the kinetics of the replacement reaction, the polymorph selection, and the crystallization pathways toward bastnasite. The findings allow to gain a more in‐depth understanding of the formation REE‐bearing carbonates, particularly the mineral bastnasite, which is the main source of REEs for industry. This knowledge can be used to improve REE separation, exploration, exploitation methods, as well to produce carbonate minerals with tailored structures.