Structural and magnetic properties of Co1−xFexSr2YCu2O7+δ compounds

Abstract

Here we study the structural and magnetic properties of the Co1−xFexSr2YCu2O7+δ compound (0≤x≤1). X-ray diffraction patterns and simulated data obtained from Rietveld refinement of the same indicate that the iron ion replacement in Co1−xFexSr2YCu2O7+δ induces a change in crystal structure. The orthorhombic Ima2 space group structure of Co-1212 changes to tetragonal P4/mmm with increasing Fe (x≥0.5) ion. The XPS studies reveal that both Co and Fe ions are in mixed states of 3+/4+ for the former and 2+/3+ in case of later. The magnetization with temperature follows Curie–Weiss behavior, in the range of 150–300 K and short magnetic correlations/spin glasslike features below 150 K. The observed magnetic behavior is due to competition of antiferro/ferromagnetic exchange interaction of Co3+ [intermediate spin (IS)]-O–Co3+ (IS)/Co4+ [low spin (LS)] and Fe3+ [high spin (HS)]-O–Fe2+ (LS)/Fe3+ (HS)/Co3+ (IS)/Co4+ (LS) states. Although none of the studied as synthesized samples in Co1−xFexSr2YCu2O7+δ are superconducting, the interesting structural changes in terms of their crystallization space groups and the weak magnetism highlights the rich solid state chemistry of this class of materials.

Role of BaO/SrO layers in deciding the electronic structure of Cu0.3Co0.7Ba2−xSrxYCu2O7+δ (CoCu-1212) x=0, 1 and 2

“…Deconvolution of Co (2p) core level spectra shows the presence of Co 3+ and Co 4+ with a satellite peak, at the binding energy of 779.50 eV and 781.20 eV for Co (2p 3/2 ) and 794.81 eV and 796.61 eV for Co (2p 1/2 ), respectively in all compositions. The similar kinds of results have also been reported in literature regarding concentration and binding energy of Co 3+/4+ [24][25][26]. Curve shows the domination of Co 3+ state over Co 4+ state for x = 0 and 1 sample, but for x = 2 both states are almost equal.…”

“…The paramagnetic nature and its magnitude is almost same for x = 0 and 1 composition but it has increased for x = 2 composition. The Co-1212 (CoSr 2 YCu 2 O 7 ) phase shows some antiferromagnetic ordering [8,24,28] near 150 K which was thought to originate by Co 3+ spin [28]. An ordering of antiferromagnetic to ferromagnetic is observed in Co 1−x Fe x Sr 2 YCu 2 O 7 with increasing Fe content [24].…”

“…In x = 2 the decrease in valance state of Cu may be due to structural changes. Since CoSr 2 YCu 2 O 7+ı is crystallize in orthorhombic Ima2 [8,[11][12][13]24]. Our x = 2 sample has 30% Cu at Co site hence it is more probable that it would be crystallized in orthorhombic Ima2 space group.…”

Structure and superconductivity in new Nb-based cuprates (Nb,Ti,Cu)Sr2EuCu2Oz

“…The same can be seen with the 113 and 123 peaks of the tetragonal phase. A similar splitting was also observed in the Co 1-x Fe x Sr 2 YCu 2 O 7þd system, in which the change in space group from P4/mmm to Ima2 appears in the XRD pattern as the Fe-doping content x decreases [13]. However, neither the fitting of the XRD data in P4/mmm space group nor such fitting in Ima2 space group resulted in an acceptable fitting result.…”

“…The increase in diamagnetic moment measured under FC conditions for similar sized samples suggests that the superconducting volume percentage increases as the Cu doping content increases. The superconducting volume percentages estimated from the density calculated from the XRD data shown in Table 1 [13]. The M-1212 phase crystallizes typically either in a tetragonal structure (P4/mmm) with MO 6 (M ¼ Nb, Ru, Fe) octahedra or in an orthorhombic structure (Ima2) with MO 4 (M ¼ Co,Ga) tetrahedra.…”