New Insights on the Electronic-Structural Interplay in LaPdSb and CePdSb Intermetallic Compounds

Multifunctional physical properties are usually a consequence of a rich electronic-structural interplay. To advance our understanding in this direction, we reinvestigate the structural properties of the LaPdSb and CePdSb intermetallic compounds using single-crystal neutron and X-ray diffraction. We establish that both compounds can be described by the non-centrosymmetric space group P6$_3$mc, where the Pd/Sb planes are puckered and show ionic order rather than ionic disorder as was previously proposed. In particular, at 300 K, the (h, k, 10)-layer contains diffuse scattering features consistent with the Pd/Sb puckered layers. The experimental results are further rationalized within the framework of DFT and DFT+ embedded DMFT methods, which confirm that a puckered structure is energetically more favorable. We also find strong correspondence between puckering strength and band topology. Namely, strong puckering removes the bands and, consequently, the Fermi surface pockets at the M point. In addition, the Pd-d band character is reduced with puckering strength. Thus, these calculations provide further insights into the microscopic origin of the puckering, especially the correspondence between the band’s character, Fermi surfaces, and the strength of the puckering

Phase Transitions and Physical Properties of the Mixed Valence Iron Phosphate Fe3_3(PO3_3OH)4_4(H2_2O)4_4

Iron phosphate materials have attracted a lot of attention due to their potential as cathode materials for lithium-ion rechargeable batteries. It has been shown that lithium insertion or extraction depends on the Fe mixed valence and reduction or oxidation of the Fe ions’ valences. In this paper, we report a new synthesis method for the Fe$_3$(PO$_3$OH)$_4$(H$_2$O)$_4$ mixed valence iron phosphate. In addition, we perform temperature-dependent measurements of structural and physical properties in order to obtain an understanding of electronic–structural interplay in this compound. Scanning electron microscope images show needle-like single crystals of 50 μm to 200 μm length which are stable up to approximately 200 °C, as revealed by thermogravimetric analysis. The crystal structure of Fe$_3$(PO$_3$OH)$_4$(H$_2$O)$_4$ single crystals has been determined in the temperature range of 90 K to 470 K. A monoclinic isostructural phase transition was found at ~213 K, with unit cell volume doubling in the low temperature phase. While the local environment of the Fe$^{2+}$ ions does not change significantly across the structural phase transition, small antiphase rotations occur for the Fe$^{3+}$ octahedra, implying some kind of electronic order. These results are corroborated by first principle calculations within density functional theory, which also point to ordering of the electronic degrees of freedom across the transition. The structural phase transition is confirmed by specific heat measurements. Moreover, hints of 3D antiferromagnetic ordering appear below ~11 K in the magnetic susceptibility measurements. Room temperature visible light absorption is consistent with the Fe$^{2+}$/Fe$^ {3+}$ mixed valence

Effect of nanometric γ´-particles on the stress-induced martensitic transformation in ⟨001⟩-oriented Co49Ni21Ga30 shape memory alloy single crystals

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Phase Transitions and Physical Properties of the Mixed Valence Iron Phosphate Fe3(PO3OH)4(H2O)4

Iron phosphate materials have attracted a lot of attention due to their potential as cathode materials for lithium-ion rechargeable batteries. It has been shown that lithium insertion or extraction depends on the Fe mixed valence and reduction or oxidation of the Fe ions’ valences. In this paper, we report a new synthesis method for the Fe3(PO3OH)4(H2O)4 mixed valence iron phosphate. In addition, we perform temperature-dependent measurements of structural and physical properties in order to obtain an understanding of electronic–structural interplay in this compound. Scanning electron microscope images show needle-like single crystals of 50 μm to 200 μm length which are stable up to approximately 200 °C, as revealed by thermogravimetric analysis. The crystal structure of Fe3(PO3OH)4(H2O)4 single crystals has been determined in the temperature range of 90 K to 470 K. A monoclinic isostructural phase transition was found at ~213 K, with unit cell volume doubling in the low temperature phase. While the local environment of the Fe2+ ions does not change significantly across the structural phase transition, small antiphase rotations occur for the Fe3+ octahedra, implying some kind of electronic order. These results are corroborated by first principle calculations within density functional theory, which also point to ordering of the electronic degrees of freedom across the transition. The structural phase transition is confirmed by specific heat measurements. Moreover, hints of 3D antiferromagnetic ordering appear below ~11 K in the magnetic susceptibility measurements. Room temperature visible light absorption is consistent with the Fe2+/Fe3+ mixed valence