Half-integer flux quantization in a superconducting loop with a ferromagnetic
π-junction
Christoph Strunk
Institute of Experimental and Applied Physics, University of Regensburg, Germany
Superconducting loops containing a π-junction are predicted to show a spontaneous magnetic moment
in zero extenal magnetic field. In order to confirm this longstanding prediction experimentally we performed magnetization measurements on individual mesoscopic superconducting Niobium loops with a
ferromagnetic (PdNi) π-junction. The loops are prepared on top of the active area of a micro Hall-sensor
based on high mobility GaAs/AlGaAs heterostructures. We observe asymmetric switching of the loop
between different magnetization states when reversing the sweep direction of the magnetic field. This is
evidence for a spontaneous current induced by the intrinsic phase shift of the π-junction. In addition,
the presence of the spontaneous current at zero applied field is directly revealed by an increase of the
magnetic moment with decreasing temperature, which results in half integer flux quantization in the loop
at low temperatures.
Sorting category: Be Superconductivity
Keywords: superconductivity, pi-junctions,, dilute ferromagnets, Hall-magnetometry
INVITED PAPER
LT2547