Coexistence of ferromagnetism and superconductivity in the hybrid ruthenate-cuprate compoundRuSr2GdCu2

C. Bernhard

¹

,

J. L. Tallon²,

Ch. Niedermayer

³

et al.

Abstract

We have investigated the magnetic and the superconducting properties of the hybrid ruthenatecuprate compound RuSr2GdCu2O8 by means of zero-field muon spin rotation-(ZF-µSR) and DC magnetization measurements. The DC-magnetisation data establish that this material exhibits ferromagnetic order of the Ru-moments (µ(Ru) ≈ 1 µB) below TCurie = 133 K and becomes superconducting at a much lower temperature Tc = 16 K. The ZF-µSR experiments indicate that the ferromagnetic phase is homogeneous on a microscopic scale and accounts for most of the sample volume. They also suggest that the magnetic order is not significantly modified at the onset of superconductivity.

A μSR study of the magnetoresistive ruthenocuprates RuSr2Nd1.8−xY0.2CexCu2O10−δ(x= 0.95 and 0.80)

“…As the temperature decreases towards T Ru ,  increases which shows that there is a decrease in the spin fluctuation rate as expected. However the critical divergence in  which is normally observed at a magnetic phase transition, and has been previously been observed at T Ru in superconducting ruthenocuprates [3,18], is not evidenced and instead  increases gradually with decreasing [9,15]. In corroboration similar cluster growth has been evidenced from μSR experiments on CMR materials Sr 2 RMn 2 O 7 [21] and is also well documented in cuprates [22].…”

Magnetism and Superconductivity in Ru1−x Sr2RECu2+x O8−d (RE=Gd, Eu) and RuSr2Gd1−y CeyCu2O8 Compounds

“…Fig. 15 (triangles) presents the temperature dependence of the internal field for RuSr 2 Interestingly, our thermogravimetric measurements did not show any noticeable changes in the oxygen content between superconducting and non-superconducting materials. Thus, we should consider that the structural differences between both compounds occur in the form of slight, but still decisive, changes of cation site defects/substitutions or in the difference in the structural distortions.…”

Superconductivity in magnetically ordered Ru1-xIr xSr2GdCu2O8 compounds

“…[6,7] The crystal structure of the RuSr 2 LnCu 2 O 8 compound (Ru-1212) is closely related to the one of the LnBa 2 Cu 3 O 7 (Ln-123), [1] in which the intermediate layer consists of vertex sharing RuO 6 octahedra replacing the CuO 4 squares of the Ln-123 structure. [4,5] The coexistence of SC and FM can be sustained possibly because of the weak coupling between the Ru-O magnetically ordered layers and the SC Cu-O planes.…”

“…[9] Another relevant feature of these superconductors is the strong dependence of parameters like the normal-state electrical resistivity (ρ), the superconducting transition temperature (T c ), and the width of the superconducting transition (∆T c ) on the synthesis conditions. [6] Nevertheless, the onset of SC (T c,onset ) for the Ru-1212 RuSr 2 GdCu 2 O 8 compound is usually ∼ 45 K and the Curie temperature T M ∼ 132 K. [4] The weak coupling that allows the coexistence of SC and FM is strongly affected by both high pressure and chemical substitutions. Thus, an approach to study the coexisting phenomena in these superconductors is via chemical substitution.…”

“…[1,2] The interest in these materials was triggered by the observation of coexisting superconductivity (SC) and long-range magnetic order, including weak-ferromagnetism (wFM), at moderately high temperatures (T). [3,4] The occurrence of long-range magnetic order has been determined by means of magnetic susceptibility, and muon spin relaxation, while details of the magnetic and crystal structure have been studied by neutron diffraction. [5] Heat capacity measurements and diamagnetic shielding fraction data indicate that SC is a bulk property, coexisting in a microscopic scale with magnetism in these materials.…”