Field-induced magnetic instability within a superconducting condensate

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Science Advances  19 May 2017:
Vol. 3, no. 5, e1602055
DOI: 10.1126/sciadv.1602055
  • Fig. 1 Magnetic order at various magnetic fields.

    The scans display diffracted neutron intensity in counts per 30 minutes (cts/30 min) along the tetragonal plane (q, q, 0.5) in reciprocal lattice units (r.l.u.). The reflections correspond to magnetic Bragg peaks at μ0H = 0, 4, 7, 8.5, 9.5, and 10.5 T for (A) to (F), respectively. Background was measured at μ0H = 12 T. All scans were taken at T = 40 mK for H||[1 Embedded Image 0]. The integrated intensity grows for increasing fields up to 4 T, decreases for further field increments, and vanishes around μ0H* ≈ 8 T. For higher fields, magnetic order reappears, increases in intensity, and collapses at μ0H = 11 T.

  • Fig. 2 Discovery of a magnetic instability inside the superconducting phase.

    The position-optimized peak intensity (red) shows two distinct magnetic phases inside the superconducting phase. Both phases vanish at μ0H* = 8.0(2) T (solid and dashed lines are guides to the eye). Because of diffuse scattering, the magnetic intensity remains above the background level (blue) in the vicinity of H*. The high-field phase collapses at the onset of the superconducting phase (resistivity along H||[1 0 0] is shown in green), μ0Hc2 =11.0(2) T, providing evidence for a coupling between superconductivity and magnetic order.

  • Fig. 3 A magnetic instability separates two magnetic phases with identical symmetry inside the superconducting condensate.

    HT phase diagram of Nd0.05Ce0.95CoIn5 for H||[1 Embedded Image 0]. The color scale represents the background-subtracted magnetic intensity. Orange circles display the magnetic phase boundaries obtained from neutron scattering results (orange dashed lines are guides to the eye). White diamonds show the superconducting phase boundary measured via electrical resistivity and heat capacity (the gray dashed line shows the superconducting phase boundary normalized from CeCoIn5). The color map reveals a field-induced instability at μ0H* = 8.0(2) T. The high-field phase, Q phase, increases linearly in intensity for increasing fields and collapses at the superconducting upper critical field μ0Hc2.

  • Fig. 4 Field-dependent wave vector and magnetic structure.

    The in-plane component of the propagation vector decreases linearly with increasing fields. Inset: Magnetic structure refined at μ0H = 0 and 10.5 T. An amplitude-modulated structure with a moment configuration perpendicular to the basal plane is found, similar to the Q phase of CeCoIn5.

Supplementary Materials

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Materials and Methods
    • fig. S1. Macroscopic results.
    • fig. S2. Temperature dependence of magnetic intensity in the critical region.
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