NMR Evidence for Coexistence of Superconductivity and Ferromagnetic Component in Magnetic SuperconductorRuSr2YCu2O8<

Abstract

From Ru- and Cu-NMR studies, we present evidence for coexistence of superconductivity and ferromagnetism in a cuprate superconductor RuSr2YCu2O8 (RuY1212). The observation of a large enhancement of a radio-frequency field for the Ru-NMR signal at zero field reveals the existence of a ferromagnetic (FM) component in the ordered RuO2 plane below a Curie temperature of TM = 150 K. Just below the onset temperature of superconductivity T(onset)c = 45 K, a remarkable decrease of the nuclear spin-lattice relaxation rate 1/T1 was observed within the ordered RuO2 plane as well as the CuO2 plane, revealing that the superconducting gap coexists with the FM component in the RuO2 plane on a microscopic scale. In addition, from the observation of a sharp peak in 101(1/T1) at T(zero)c approximately 23 K where the resistivity becomes zero, we suggest that the motion of self-induced vortices originating from fluctuations of the FM component induces the resistivity between T(onset)c and T(zero)c in RuY1212.

Magnetic transitions and ferromagnetic clusters inRuSr2(Eu,Ce)Xue1, Lorenz2, Cao3 et al. 2003Phys. Rev. B325350View full textAdd to dashboardCite

“…The zero-field NMR data suggest that the aligned moment of Ϸ1.6 B /Ru should be perpendicular to the c axis instead and that the FM component should be a large part of the moment. 6 While at least two other NPD studies claim similarly negligible FM components, 7,8 both the large FM moment and the perpendicular spin direction were confirmed by independent NMR measurements. 9 These conflicts will be difficult to reconcile, in our opinion, if these ruthenocuprates are microscopically homogeneous.…”

“…[1][2][3][4][5][6] Even in the relatively simple case of Ru1212, a large discrepancy exists. A NPD investigation reported that the Ru spins ordered antiferromagnetically ͑AFM͒ along the c axis with a rather stringent upper limit of (0.1,0.2) B /Ru at Hϭ0 and 7 T, respectively, for the ferromagnetic ͑FM͒ components of Ru.…”

Magneto-superconductivity of 100-atm O2-annealed RuSr2Gd1.5Ce0.5Cu2O10−δ

“…The appearance of bulk superconductivity at low temperatures in Ru-1212 was initially criticised [11] which was later refuted [12,13]. Also not all single phase Ru-1212 exhibit the co-existence of superconductivity and magnetism [14].…”

Oxygen nuclear magnetic resonance study of RuSr2EuCu2O8

“…However, there is an additional complication in that the crystallite domain size is small and there are coherent rotations of the RuO 6 octahedra about the c-axis leading to a superstructure and subdomains of 5 nm to 20 nm in diameter [5,8]. It has been suggested on the basis of transport, heat capacity and microwave measurements that the electronic behavior of RuSr 2 RCu 2 O 8 is similar to an underdoped HTSC [6,18] However, nuclear magnetic resonance (NMR) measurements have been interpreted in terms of RuSr 2 RCu 2 O 8 being comparable to an optimally doped HTSC [24].…”