Sc doping of MgB2: the structural and electronic properties of Mg1−xScxB2

Effects on transition temperature and Raman spectra of substitution of Cr and Al for Mg in MgB2

“…2. For comparison, the Sc content dependence of the lattice parameters of a-and c-axes and cell volume V, c/a reported by Agrestini et al [17] is shown in Fig. 2 simultaneously.…”

“…The investigation of lattice effects on T c has also been attempted by applying hydrostatic pressure in crystalline MgB 2 , due to the limited response of solid MgB 2 to pressure, however, the lattice variation is too small to present the structural effects. In order to explore the influence of charge density on the electronic properties, considering that Sc and Mg have nearly the same atomic radius with a minimum effect on the structure size, Agrestini et al [17] have synthesized and investigated the effect of Sc doping on the superconducting properties of MgB 2 . They argued that the holes in the boron σ-bands play an essential role for the occurrence of superconductivity in the diborides.…”

“…Besides, the change of the c/a ratios of the Cr-and Sc-doping samples is little, while the c/a ratio of the Al-doping samples evidently decreases, as the dopant content increasing, which indicates hardly compressible B-B σ-bonds and interlayer distances sensitive to the intercalated cation [20]. Figure 4 shows the M content dependence of T c for the Mg 1-x M x B 2 (M = Cr, Al) samples obtained from the measurements of the low-temperature resistance and compare with the T c of Sc-doping samples [17], which reveal a systematic change of T c with the doping of Cr, Al or Sc, in other words, the T c of all the doping samples decreases as the doping content increasing. It is known that the charge carries in MgB 2 are holes.…”

The loss of anisotropy in MgB2with Sc substitution and its relation with the critical temperature

“…Agrestini et al 7,8 measured T c as function of scandium content in (Mg 1-x Sc x )B 2 ; the values of the second paper 8 are reproduced in figure 2b (the absence of values in the 0.02 and 0.12 range, is due to a miscibility gap). This coincides with the argument of Agrestini et al that the reduction of T c can be associated to a 2D/3D electronic transition, although they call it an electronic topological transition (ETT).…”

Two-Dimensional Nanogranularity of the Oxygen Chains in the YBa2Cu3O6.33 Superconductor

“…Thus, the study of local features by using high resolution experimental probes assumes a paramount importance for the a deeper understanding of new complex and heterogeneous materials. Local probes such as X ray Absorption experimental methods (XANES and EXAFS) and high resolution X ray and neutron diffraction have been used for investigating structural inhomogeneity in various systems such as diborides [15][16][17] and cuprates [18][19][20]. In the last years, the possibility to focus X ray beam onto micrometric and sub-micrometric areas, has allowed to probe the local structure with high resolution in…”