Search

The electric field gradient on different Fe sites in Fe-doped 124 superconductor is calculated by the point-charge-effective-valence model. Ion valences and electronic field gradient showing the lattice displacement of Fe ion for different Fe clusters are related. Fe is displaced from CuO2 planes toward the apical O(1) site.

The article explains the synthesis and the various structural and magnetic properties of the different two-dimensional triangular lattice Li[VO.sub.2] compounds. An increase in the x in the compound is shown to lead to a significant reduction in the magnetic phase transition temperature.

An investigation on the magnetic properties of perovskite-type manganese oxide with double Mn-O layers of composition La(sub 2-2x)Sr(sub 1+2x)Mn(sub 2)O(sub 7) (x = 0.33 and 0.4) is conducted. The distinct curvilinear shape of -deltaS(sub M) for perovskites with double Mn-O layers show different magnetic mechanisms arising from magnetocrystalline anisotropy.

Transition metal compounds with two-dimensional triangular lattice, such as LiVO2, are of particular interest, because they exhibit peculiar structural and magnetic behavior involving the frustration present in these oxides. An orbital ordering transition occurs near 500 K, which leads to a suppression of magnetic moment below the phase transition temperature Tt. We synthesized a series of Mg-doped LiVO2 single-phase samples and reported their structural and magnetic properties. The samples were characterized by x-ray diffraction, scanning electron microscope, differential scanning calorimetry, electrical resistivity, magnetic susceptibility, and specific heat measurement. For Mg-doped samples Li1-xMgxVO2 (x=0, 0.05, 0.10, and 0.15), the structural analysis show that, with increasing x, the lattice constants change monotonously; in the a-b plane, the lattice expands; while in the c-axis direction, the lattice is compressed. Substitution of Li with Mg ions results in the degeneration of two-dimensional characteristics and the distortion of the VO6 block, which significantly influence magnetic properties. The magnetic phase transition temperature falls with increasing x. The Mg-dopants play an important role on breaking the original moment equilibrium and suppressing the magnetic frustration. [ABSTRACT FROM AUTHOR]

Magnetocaloric properties of perovskite-type manganese oxides with double Mn-O layers of composition La2-2xSr1+2xMn2O7 (x=0.33 and 0.4) have been investigated. A broad peak of magnetic entropy change (-ΔSM) was observed at the Curie temperature. The shape of -ΔSM is strongly dependent on the Sr concentration. In contrast to Ln1-xAxMnO3 perovskites, the distinct curvilinear shape of -ΔSM for perovskites with double Mn-O layers shows different magnetic mechanisms arising from magnetocrystalline anisotropy. [ABSTRACT FROM AUTHOR]

Magnetocaloric properties of perovskite-type manganese oxides with double Mn-O layers of composition La2-2xSr1+2xMn2O7 (x=0.33 and 0.4) have been investigated. A broad peak of magnetic entropy change (-ΔSM) was observed at the Curie temperature. The shape of -ΔSM is strongly dependent on the Sr concentration. In contrast to Ln1-xAxMnO3 perovskites, the distinct curvilinear shape of -ΔSM for perovskites with double Mn-O layers shows different magnetic mechanisms arising from magnetocrystalline anisotropy. [ABSTRACT FROM AUTHOR]