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Magnetic properties and electronic structures of NdFeO3 have been studied by performing accurate first principle calculation based on density functional theory. The 4f-electrons of Nd are explicitly treated as valence electrons. The simulation results of crystal structure and magnetic structure of this compound agree well with the experimental observations. Importantly, our study indicates that the spin reorientation transition of Fe3+ spin sublattice can be ascribed to the exchange interaction between Nd-4f and Fe-3d electrons, which are mediated by O2-2p state in Fe-O plane. As the temperature decreases, the Fe-O and Nd-O bonds become more covalent, and the exchange interactions become stronger.

We report a comparative study of the critical current density (Jc) and vortex pinning among pure and Mn doped KxFe2−ySe2 single crystals. It is found that the Jc values can be greatly improved by Mn doping and post-quenching treatment when comparing to pristine pure sample. In contrast to pure samples, an anomalous second magnetization peak (SMP) effect is observed in both 1% and 2% Mn doped samples at T = 3 K for H∥ab but not for H∥c. Referring to Dew-Hughes and Kramer's model, we performed scaling analyses of the vortex pinning force density vs magnetic field in 1% Mn doped and quenched pristine crystals. The results show that the normal point defects are the dominant pinning sources, which probably originate from the variations of intercalated K atoms. We propose that the large nonsuperconducting K-Mn-Se inclusions may contribute to the partial normal surface pinning and give rise to the anomalous SMP effect for H∥ab in Mn doped crystals. These results may facilitate further understanding of the superconductivity and vortex pinning in intercalated iron-selenides superconductors.

The PGPR strains Sinorhizobium sp. A15, Bacillus sp. A28, Sphingomonas sp. A55, and Enterobacter sp. P24 were isolated from the maize rhizosphere in Northeast China and inoculated separately; Inoculation of these strains significantly enhanced maize growth, and the strains A15, A28, and A55 significantly increased grain yield by as much as 22%–29%; Inoculation of these strains increased the abundance and species richness of bacteria in the maize rhizosphere, and the relative abundance of Acidobacteria_Subgroup_6, Chloroflexi_KD4‐96, and Verrucomicrobiae at the class level and Mucilaginibacter at the genus level were positively correlated with maize biomass and yield.

Fe1.01Se0.38Te0.62 single crystal was successfully grown by self-flux method, and effect of post-annealing technique on structure and superconductivity was also systemically studied. The results show the as-grown sample has an excellent superconductivity with an onset transition temperature Tconset ∼ 14.6 K and a zero resistivity temperature Tczero ∼ 13.4 K. After annealing at 400 °C for 48 h, excess Fe in the post-annealing sample appears with Fe1.06Se0.34Te0.66 formula, and superconductivity was strongly suppressed with Tczero ∼ 8.0 K. The experiments found that excess Fe is located at Fe(2) site with local magnetic moment. According to the Werthamer-Helfand-Hohenberg (WHH) theory, the upper critical fields Hc2 at zero temperature were estimated to be 54.2 T for as-grown sample and 28.2 T for post-annealing sample. Two abnormal drops in DC magnetization are found near 40 K and 125 K for all samples, the one near 40 K may be related to a spin freezing of excess Fe and that near 120 K should be corresponding to the structural transition from tetragonal to monoclinic. This is confirmed by the strain measurement. On the other hand, a kink change of specific heat was also found around 10 K for a post-annealed sample.

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