Coexistence of long-range magnetic ordering and singlet ground state in the spin-ladder superconductor SrCa13Cu24O41<

Abstract

A long-range magnetic order was discovered in the quasi-one-dimensional spin-ladder compound SrCa 13 Cu 24 O 41 by susceptibility, specific heat, and neutron diffraction experiments. The temperature dependence of the magnetic Bragg peak intensity could be well fitted to the power law with a transition temperature T N = 4.23 K and a critical exponent β = 0.28, indicating a three-dimensional phase transition for a low-dimensional magnet. A computer program was coded and found two possible magnetic structure models fitting best with all the observed magnetic peaks. These models suggest the spin-ladder sublattice is magnetically ordered with Cu moments aligning along the a axis. The spin interactions are primarily antiferromagnetic along rungs and legs, while there are ferromagnetic clusters along legs. Surprisingly, the singlet-triplet spin-gap excitation is observable above and below T N , indicating a coexistence of the spin-singlet ground state and long-range magnetic ordering state in this compound.

Spin dynamics of edge-sharing spin chains in SrCa13Cu24O41

“…Both the spin-ladder and spin-chain subsystems in SrCa 13 Cu 24 O 41 are quasi-1D or 1D magnetic systems. Our previous inelastic neutron-scattering experiment confirmed the spin-gap excitation at ∼32 meV in this compound [16,17]. This excitation was attributed to the spin ladder due to its consistency with most other results reported for the spin ladders in the parent compound [22,32].…”

“…First, holes transfer to the ladder sublattice, which makes hole pairing possible as described in the theory. Second, we confirmed that the spin gap, which is the driving force for the hole pairing, still exists at ∼32.5 meV in highly Cadoped compounds [17]. The high pressure could play another critical role in changing the ratio J R /J L from less than 1 to larger than 1 by distorting the lattice even though our previous measurement of the spin gap under a hydrostatic pressure of 2 GPa was inconclusive due to the challenges of the experiments [25].…”

“…Our inelastic neutron-scattering experiments revealed that the increase of Ca doping did not close the spin gap of the spin ladder in all these compounds, but only suppressed its intensity due to the increase of hole doping [16]. In the highly doped compound SrCa 13 Cu 24 O 41 , long-range magnetic ordering has been observed and the coexistence of magnetic ordering and a spin-liquid ground state was demonstrated [17]. All these studies provide some answers to the interesting questions mentioned above.…”

“…For example, Rb 2 MnO 4 orders into the antiferromagnetic phase at 38.4 K [35]. In contrast, SrCa 13 Cu 24 O 41 becomes antiferromagnetic ordering at 4.2 K [17], indicating a much weaker interplane interaction.…”

S=12quantum critical spin ladders produced by orbital ordering inBa2CuTeO6

“…Previous examples in the literature of ordering in S = 1 2 ladders or chains have involved clear signatures such as sharp anomalies in heat capacity [11,[32][33][34] and divergent peaks in NMR 1/T 1 [35,36]. In ladder materials with field-induced magnetic…”