Antiferromagnetic semiconductor Eu3Sn2P4 with Sn–Sn dimer and crown-wrapped Eu

A novel antiferromagnetic semiconductor, Eu3Sn2P4, has been discovered. Single crystals of Eu3Sn2P4 were prepared using the Sn self-flux method. The crystal structure determined by single crystal X-ray diffraction shows that Eu3Sn2P4 crystallizes in the orthorhombic structure with the space group Cmca (Pearson Symbol, oP216). Six Sn–Sn dimers connected by P atoms form a Sn12P24 crown-shaped cluster with a Eu atom located in the center. Magnetization measurements indicate that the system orders antiferromagnetically below a TN ∼14 K at a low field and undergoes a metamagnetic transition at a high field when T \u3c TN. The effective magnetic moment is 7.41(3) μB per Eu, corresponding to Eu2+. The electric resistivity reveals a non-monotonic temperature dependence with non-metallic behavior below ∼60 K, consistent with the band structure calculations. By fitting the data using the thermally activated resistivity formula, we estimate the energy gap to be ∼0.14 eV. Below TN, the resistivity tends to saturate, suggesting the reduction of charge-spin scattering

Pd-P antibonding interactions in A Pd2 P2 (A = Ca and Sr) superconductors

We report the observation of superconductivity in single-crystalline CaPd2P2 and SrPd2P2 obtained from Bi-flux. Both CaPd2P2 and SrPd2P2 crystallize in the ThCr2Si2-type structure (space group I4/mmm) with a short P-P distance. Electrical resistivity and specific heat measurements conjointly corroborate bulk superconductivity at Tc∼1.0 K with ΔC/γTc=1.42 for CaPd2P2, and Tc∼0.7 K with ΔC/γTc=1.47 for SrPd2P2. The electronic structure calculations and chemical bonding analysis indicate that Pd-P antibonding interactions primarily dominate around the Fermi level and play the critical role in inducing superconductivity

Crystal Symmetry and Physical Properties of Selected Intermetallic Compounds

Intermetallic compounds exhibit various interesting phenomena, such us superconductivity and non - trivial topology, which are usually dictated by the interplay of crystal symmetry, spin - orbit coupling, electron – electron and electron – phonon interactions. This dissertation presents the experimental study of interesting phenomena observed in Pd - P – based, and Eu - based compounds due to the interplay between various degrees of freedom. For Pd-P-based compounds, we find that CaPd2P2 and SrPd2P2 crystallize in a tetragonal space group I4/mmm and exhibit superconductivity below Tc = 1.0 K and 0.7 K, respectively. The antibonding interaction between Pd and P orbitals play a critical role in inducing superconductivity. On the other hand, CaPd1-xP1+x and SrPd1-xP1+x form a honeycomb lattice: one is centrosymmetric and another non-centrosymmetric, respectively. Our study indicates that it is necessary to mix Pd and P site within honeycomb lattice to stabilize the crystal structure. Both compounds are diamagnetic materials and exhibit metallic behavior. For Eu-based compounds, involving f – electrons, magnetism will play an important role. We discovered a new magnetic semiconductor Eu3Sn2P4, which shows an antiferromagnetic transition at TN = 14 K, and semiconducting behavior with the energy gap of 0.14 eV. Eu can also bring the magnetism into the topologically non-trivial materials, which motivated us to study EuZn2As2, an analogue to EuCd2As2. EuZn2As2 exhibits an A - type antiferromagnetic ordering below TN = 19 K, with strong ferromagnetic fluctuations up to Tfl ~ 200 K. Since the TN and Tfl are two times higher than that for EuCd2As2, it provides a better platform for exploring topological properties in both the magnetically ordered and fluctuation regimes. The high magnetic field resistivity data show giant magnetoresistance (MR) unsaturated up to 60 T and Shubnikov-de Haas quantum oscillations with a single frequency of F = 38 T. Quantitative data analysis indicates that the corresponding hole band has a non - trivial Berry phase and reaches the first Landau level at ~50 T, thus exhibiting linear MR in the quantum limit

Quantum-limit phenomena and band structure in the magnetic topological semimetal EuZn2As2

Abstract The interplay between magnetism and electronic topology in the quantum limit is a forefront subject of condensed matter physics. Here, we show the electronic and magnetic properties of layered antiferromagnet EuZn2As2 in pulsed magnetic fields up to 60 T and temperatures down to 0.6 K. By analyzing the quantum oscillations observed in the magnetoresistance (MR) and proximity detector oscillator (PDO) frequency, we find that (1) the oscillation frequency F = 46 ± 6 T for H // c and 42 ± 2 T for H // ab; (2) the corresponding Berry phase is close to π for H // c, implying a nontrivial topology; and (3) the large linear MR occurs beyond the first Landau level, without any sign of saturation. From these observations, we conclude that the linear MR can be understood by considering diffusing cyclotron centers due to compressed Landau wavefunction, an emergent behavior in the quantum limit

Antiferromagnetic semiconductor Eu3Sn2P4 with Sn–Sn dimer and crown-wrapped Eu

A novel antiferromagnetic semiconductor, Eu3Sn2P4, has been discovered. Single crystals of Eu3Sn2P4 were prepared using the Sn self-flux method. The crystal structure determined by single crystal X-ray diffraction shows that Eu3Sn2P4 crystallizes in the orthorhombic structure with the space group Cmca (Pearson Symbol, oP216). Six Sn–Sn dimers connected by P atoms form a Sn12P24 crown-shaped cluster with a Eu atom located in the center. Magnetization measurements indicate that the system orders antiferromagnetically below a TN ∼14 K at a low field and undergoes a metamagnetic transition at a high field when T TN. The effective magnetic moment is 7.41(3) μB per Eu, corresponding to Eu2+. The electric resistivity reveals a non-monotonic temperature dependence with non-metallic behavior below ∼60 K, consistent with the band structure calculations. By fitting the data using the thermally activated resistivity formula, we estimate the energy gap to be ∼0.14 eV. Below TN, the resistivity tends to saturate, suggesting the reduction of charge-spin scattering.</p

Novel vitamin D3-hydroxyderivatives as candidates for the therapy against skin-aging and photo-aging: bioinformatical analysis

Vitamin D3 acts through its most active form, calcitriol, 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3] as agonist of one of the receptors involved in this ligand action, vitamin D receptor (VDR), which is also a transcription factor. Numerous modifications of calcitriol at its side-chain, C-ring, A-ring, triene system, alone or in combination, as well as nonsteroidal mimics provided new VDR agonists and some antagonists with biological activity and possible therapeutical potential. Some of the D3 metabolites, including 20,23(OH)2D3 and 20(OH)D3 are able to inhibit RORE-mediated transactivation, as well as the interaction between the RORα/γ ligand-binding domain (LBD) with an LXXLL coactivator peptide. Our analysis of recently reported microarray data on vitamin D3 (D3) induced changes in cultured human keratinocytes indicated that D3 hydroxyderivatives stimulate the expression of genes involved in anti-aging activities. Furthermore, we noted upregulation of the kallikrein gene family by 1,25(OH)2D3 after 24-hour treatment, including stimulation of KLK6, KLK13, KLK3, KLK9, KLK5, KLK7, and KLK10. Also, after 6-hour incubation with 1,25(OH)2D3, the upregulation of KLK6, KLK13, and KLK3 was seen.  Interestingly, ACEIs administered to hypertensive rats doubled the lifespan of these animals. In humans, ACEIs prevent hallmarks of aging, such as organ fibrosis and cardiac hypertrophy. We noted also that vitamin D3-hydroxyderivatives act against oxidative stress through upregulation of thioredoxin reductase (TXNRD1) and heme reductase-1 (HMOX-1) gene expression in keratinocytes treated for 24h. Another mechanism of anti-aging properties of inverse agonist RORa/γ is the resolution of inflammation caused by T helper (Th17) lymphocytes and switching the immune response into T regulatory (Treg) lymphocytes activation, with silencing of the inflammation state and reducing the inflammation process. The gene connected with inflammatory response, AKR1C3 (which encodes prostaglandin F synthase) is also strongly downregulated by 20,23(OH)2D3 in keratinocytes after incubation for 24 h. We suggest that vitamin D3 analogs, such as 20,23(OH)2D3, 1,25(OH)2D3, and 20(OH)D3 may have anti-aging properties through action on different pathways connected with DNA repair

Pd-P antibonding interactions in A Pd2 P2 (A = Ca and Sr) superconductors

We report the observation of superconductivity in single-crystalline CaPd2P2 and SrPd2P2 obtained from Bi-flux. Both CaPd2P2 and SrPd2P2 crystallize in the ThCr2Si2-type structure (space group I4/mmm) with a short P-P distance. Electrical resistivity and specific heat measurements conjointly corroborate bulk superconductivity at Tc∼1.0 K with ΔC/γTc=1.42 for CaPd2P2, and Tc∼0.7 K with ΔC/γTc=1.47 for SrPd2P2. The electronic structure calculations and chemical bonding analysis indicate that Pd-P antibonding interactions primarily dominate around the Fermi level and play the critical role in inducing superconductivity.</p

Low-Dimensional Magnetic Semimetal CrAlSe

While exploring novel magnetic semiconductors, the new phase CrAlSe was discovered and characterized by both structural and physical properties. CrAlSe was found to crystallize into orthorhombic CrGeTe-type structure with space group (no. 62). Vacancies and mixed occupancies were tested, and the results show that one of the 4 sites accommodates a mixture of Cr and Al atoms, while the other 4 site is fully occupied by Al atoms. Unique structural features include a T-shaped channel network created from the edge-sharing Cr/Al@Se and Al@Se polyhedra and a zipper effect of the puckered Se atoms inside the columnar channels. The round peak observed in the temperature-dependent magnetic susceptibility (χ) plot at ∼8(1) K corresponds to the antiferromagnetic-type transition in CrAlSe. However, the positive θ indicates an additional ferromagnetic interaction, which is highly likely due to the complex magnetic structure arising from the mixed Cr/Al occupancies on the 4 site. Electrical resistivity measurements confirm that CrAlSe is a semimetal with a positive magnetoresistance. Here we present the characterization and determination of the crystal structure and physical properties for this new material

Mn-induced spin glass behavior in metallic IrSnMn

Transition metal stannides are usually semiconductors with a narrow band gap. We report experimental investigation on metallic IrSnMn(= 0 and 0.56). Single crystal x-ray diffraction refinement indicates that IrSnMncrystals form a cubic structure (space group3̄) with the lattice parameter= 9.362(4) Å for= 0 and 9.328(6) Å for= 0.56. The electrical resistivity shows metallic behavior between 2 K and 300 K withdependence at\u3c 30 K for= 0, reflecting the Fermi-liquid ground state. While IrSnexhibits weak diamagnetism, partial substitution of Sn by Mn results in spin glass behavior in IrSnMnbelow∼ 13 K for= 0.56. Remarkably, an upturn in the resistivity is observed in= 0.56 below ∼2, suggesting strong spin fluctuation. This fluctuation is suppressed by the application of magnetic field, which is reflected in the observation of negative magnetoresistance. The unusual properties that emerge due to Mn doping are discussed

Thermal, Physical, and Optical Properties of the Solution and Melt Synthesized Single Crystal CsPbBr₃ Halide Perovskite

Inorganic lead-halide perovskite, cesium lead bromide (CsPbBr3), shows outstanding optoelectronic properties. Both solution- and melt-based methods have been proposed for CsPbBr3 crystal growth. The solution-based growth was done at low-temperature, whereas the melt-based growth was done at high-temperature. However, the comparison of optical, physical, and defect states using these two different growth conditions has been scarcely studied. Here, we have compared the thermal and optical properties of solution-grown and melt-grown single crystals of CsPbBr3. Positron Annihilation Lifetime Spectroscopy (PALS) analysis showed that melt-grown crystal has a relatively smaller number of defects than the chemical synthesis method. In addition, crystals grown using the chemical method showed a higher fluorescence lifetime than melt-grown CsPbBr3