Investigation of superconductivity by magnetic force microscopy

From QCLab
Prof. Jeehoon Kim (POSTECH)
  • Speaker: Prof. Jeehoon Kim (POSTECH)
  • Date: Wednesday, April 12, 2017, at 17:00
  • Place: BK Seminar Room

We have constructed a ³He magnetic force microscope (MFM), operating within a vector magnet with the base temperature of 300 mK and magnetic field range of 2-2-9 T in the x-y-z direction. We demonstrated magnetic imaging capabilities at very low temperature by imaging simultaneously superconducting vortices and magnetic stripes at T= 500 mK in the ferromagnetic superconductor ErNi₂B₂C which has a ferromagnetic transition below Twfm=2.3 K. The direct visualization of coexistence between superconductivity and magnetism was carried out in ErNi₂B₂C. The vector field performance of the apparatus was also demonstrated by the creation and imaging of Abrikosov vortices within a superconducting Nb film using a vector field. For example, an in-plane field allows creating a vortex-antivortex pair which is confined through a single flux tube, and thus showing a linear potential in distance. The 3D-magnet MFM also allows us to measure the paring symmetry of superconductors by MFM via Meissner force detection. We will show anisotropic angular dependence on the magnetic penetration depth in CeCoIn5, which signals the d-wave paring symmetry.​