H. X. Yang

Structural properties and superconductivity of SrFe2As2 − xPx (0.0 ≤ x ≤ 1.0) and CaFe2As2 − yPy (0.0 ≤ y ≤ 0.3)

The SrFe(2)As(2 - x)P(x) (0.0 ≤ x ≤ 1.0) and CaFe(2)As(2 - y)P(y) (0.0 ≤ y ≤ 0.3) materials were prepared by a solid-state reaction method. X-ray diffraction measurements indicate that the single-phase samples can be successfully obtained for SrFe(2)As(2 - x)P(x) (0.0 ≤ x ≤ 0.8) and CaFe(2)As(2 - y)P(y) (0.0 ≤ y ≤ 0.3). Visible contraction of the lattice parameters is determined due to the relatively smaller radius of P ions in comparison with that of As. The spin-density-wave (SDW) instability associated with the tetragonal to orthorhombic phase transition is suppressed noticeably in both systems following the increase in P content. The highest superconducting transitions are observed at about 27xa0K in SrFe(2)As(1.3)P(0.7) and at about 13xa0K in CaFe(2)As(1.925)P(0.075), respectively. Structural analysis suggests that lattice contraction could notably affect the superconductivity in these materials.

Pressure effects on multiferroic LuFe2O4

This letter reports that both ac susceptibility and electronic transport measurements of the multiferroic compound LuFe2O4 under pressure show that the transition temperature from the paramagnetic state to the ferrimagnetic state decreases with increasing pressure, indicating that the pressure favors the paramagnetic state and suppresses the ferrimagnetic state. Moreover, the minimum of resistivity changes under pressure, which decreases with increasing pressure, appears at the magnetic phase transition temperature.

Photoluminescence in electronic ferroelectric Er1-xYbxFe2O4

Strong Stark splitting, which is nearly independent of the R-ions replacement, has been observed through the photoluminescence investigation of electronic ferroelectric Er1−xYbxFe2O4 (x=0, 0.8, 0.9, and 0.95). Initially multiple radiative decay channels have been investigated, especially the visible transition F49/2→I415/2, of which a quenching effect has been observed. A series of small non-Raman peaks have been observed superimposed on a broadband photoluminescence spectrum, of which we tentatively assign Stark splitting to be the cause. The splitting of the F49/2 and I415/2 levels is found to be 54 meV and 66 meV, respectively. This unusually large Stark splitting at visible range indicates the existence of strong local field originated from the W-layer in the charge-frustrated ErFe2O4.