119SnMössbauer spectroscopy in the magnetic superconductor(Ru,

Abstract

The 119 Sn Mössbauer spectra for the (Ru 1Ϫx Sn x )Sr 2 GdCu 2 O 8 system, with nominal compositions xϭ0.05-0.30, were measured from room temperature down to 4.2 K in samples exhibiting magnetic order followed by a resistive superconducting transition on cooling. Two contributions to the spectra are observed in the samples at room temperature: a doublet, dominating at low x, and a singlet, probably coming from the impurity phase SrSnO 3 . A part of the doublet evolves into a magnetic structure at low temperatures and is identified to sense the matrix properties. The isomer shift indicates that Sn enters into the RuO 2 layers as Sn 4ϩ . The appearance of a magnetic phase, in the spectra, matches with the onset of the Ru-sublattice long-range order, as detected by susceptibility measurements. The area of this component exhibits a smooth decrease with the increase in the Sn content, which is well described by a random distribution in the (Ru, Sn)O 2 layers. An average in-plane transferred hyperfine field of 4.29 T was sensed at 4.2 K for the sample with xϭ0.05, gradually decreasing with an increase in x. This high value may be indicative of the emergence of a -phase state for the superconducting order parameter across the magnetically ordered planes, with low pair-breaking effects.

Study of the crystal structure, superconducting and magnetic properties of Ru1−xFexSr2GdCu2O8

“…Therefore, the above mentioned magnetic behavior is not due to a structural change, but to a weakening of the magnetic interaction between the Ru magnetic moments of the Ru sublattice. This behavior was also observed when Ru is substituted by other elements [13][14][15][16][17]. At temperatures below 40 K the M(T) curves show an increase due to the paramagnetic contribution of the Gd ions.…”

“…Several studies of cation substitutions in the Ru-1212 compound have been reported in the literature [13][14][15][16][17][18][19][20]. Their effects in the superconducting and magnetic properties depend on the type of cation and the substitutional site.…”

“…Their effects in the superconducting and magnetic properties depend on the type of cation and the substitutional site. Studies in the Ru 1-x Sn x -1212 system [13,14] show that the Sn doping suppresses the ferromagnetic moment in the RuO 2 layer, decreasing T M but, on the other hand, T c increases with the increase of Sn content. These results were attributed to the diamagnetic properties of Sn ions that reduce the total magnetic moment in the RuO 2 layers and increase the hole transfer to the CuO 2 layers.…”

Lower critical field and intragrain critical current density in the ruthenate-cuprate RuSr2Gd1.5Ce0.5Cu2O10

“…Since the discovery of the so called magnetic superconductors RuSr 2 RCu 2 O 8 (Ru-1212) and RuSr 2 (R,Ce) 2 Cu 2 O 10−δ (Ru-1222), with R=Gd, Eu, 1,2 considerable effort has been devoted to the understanding of the interplay between the ferromagnetic (FM) component, emerging from the long-range order of the Ru moments, and the onset of the superconducting (SC) state. 3 Among several important topics, the possibility of π-phase formation across the RuO 2 layers, 4,5,6 the itinerant or localized character of the magnetism of the Ru moments, 7,8,9 the magnetic phase separation scenario of nanoscale FM clusters with superconductivity nucleating only in the surrounding antiferromagnetic matrix, 10,11 and the possibility of triplet paring, 8 have been considered to explain how this puzzling coexistence may occur. On the other hand, some important superconducting parameters have been less thoroughly investigated.…”

Mössbauer study of the (Ru1-xFex)Sr2GdCu2O8-δ system and two of its possible impurities: SrRuO3 and Gd2CuO4

“…In the strive to find new superconductor materials, many studies have been done in which one or more of the elements present in the different superconductor families are substituted by others. It has been found that the substitution of a fraction of the Cu atoms by other 3d-metals rapidly downgrades the T c of the RE-123 and RE-124 families, especially if the substitution takes place in the CuO 2 planes [7,[15][16][17][18][19][20], so it is important to determine where the 3d-metal atoms go to in the superconductor structure.…”