Coexistence of ferromagnetism and superconductivity in single-phase Bi3Ni nanostructures


Coexistence of ferromagnetism and superconductivity in single-phase Bi3Ni nanostructures

Herrmannsdörfer, T.; Skrotzki, R.; Wosnitza, J.; Köhler, D.; Boldt, R.; Ruck, M.

Superconductivity and magnetic order, two fundamental ground states of condensed matter, are observed to be competitive in many materials. In the case of predominantly ferromagnetic exchange interactions, superconductivity is suppressed in almost any representative. The quantity of materials, however, in which a coexistence of superconductivity and ferromagnetism might be studied, could be larger than ever thought.
Here we demonstrate the coexistence of superconductivity and ferromagnetism in Bi3Ni nanostructures which have been prepared by making use of novel chemical-reaction paths. We have characterized their magnetic and superconducting properties by means of magnetometry and electrical-transport measurements. Other than in bulk geometry, submicron-sized particles and quasi one-dimensional nanoscaled strains of single-phase Bi3Ni undergo ferromagnetic order [1]. Superconductivity in confined Bi3Ni emerges in the ferromagnetically ordered phase and is stable up to remarkably high magnetic fields. Uniquely, ferromagnetic hysteresis at zero resistance is observed in nanostructured Bi3Ni. As a result, a magnetic hysteresis loop occurs while the material is in the superconducting state.
The coexistence of superconductivity with ferromagnetic order would most likely be possible in the case of triplet pairing. The absence of an inversion center of the lattice of confined Bi3Ni would allow for the formation of an antisymmetric spatial component of the electron-wave function and could lead to a significant admixture of a spin-triplet component of the order parameter. However, as the lattice of bulk Bi3Ni is centrosymmetric, the question remains as to whether the loss of structural long-range order at the surface of confined nanostructures could induce antisymmetry of the charge carrier wave function. Nuclear magnetic resonance experiments in high magnetic fields* may now open a chance to get deeper insight in the symmetry of the superconducting wave function in k space.

  • Invited lecture (Conferences)
    International Conference "Resonances in Condensed Matter", 21.-25.06.2011, Kazan, Russia

Permalink: https://www.hzdr.de/publications/Publ-15902
Publ.-Id: 15902