Real-Time Magneto-Optical Imaging of Vortex Lattice Oslo Superconductivity Lab

    Resolving Individual Vortices:   static images, vortex dynamics
    Movies of Vortex Dynamics:   vortex entry, vortex entry with annihilation
     Comparison with other techniques
    Interaction with a Bloch Wall:  generating vortices, manipulating vortices

    Publications:    Real-time magneto-optical imaging of vortices in superconducting NbSe2, P.-E. Goa et al. SuST 14, 729 (2001)
    Manipulation of vortices by magnetic domain walls, P.-E. Goa et al. APL 82, 79 (2003)
    Magneto-optical imaging setup for single vortex observation, P.-E. Goa et al. RSI 74, 141 (2003)
    Magneto-optic imaging of single vortex dynamics in NbSe2 crystals, M. Baziljevich et al. Adv. Sci. Tech. 38, 377 (2003)
    Single vortices observed as they enter NbSe2, A. A. F. Olsen et al., Physica C 408-410, 537 (2004)
    Interaction between superconducting vortices and Bloch wall in ferrite garnet film, J. I. Vestgarden et al., Phys. Rev. Lett. 98, 117002 (2007)

Resolving Individual Vortices

Static images

The magneto-optical imaging technique has been improved to enable observation of magnetic vortices in type-II superconductors. The main advantage of the method is its high temporal resolution combined with the applicability to any superconducting sample with a flat surface.

Vortex lattice in NbSe2 superconductor, H=3 Oe Abrikosov lattice in superconductor, H=7 Oe

Magneto-optical images of vortices in a NbSe2 superconducting crystal at 4.3 K after cooling in magnetic field of 3 and 7 Oe.  PDF

This image is used in the Illustrated Presentation for the Nobel Prize in Physics 2003. See also Gallery of Abrikosov lattices obtained by different techniques.

Dynamics of Vortices in superconductor   Vortex dynamics

The image shows the change in flux distribution over a 1 sec. time interval after a 4 mOe increase in the applied field. Dark and bright spots represent initial and final vortex positions, respectively. Medium brightness corresponds to unchanged flux distribution, indicating stationary vortices. The inset shows a close up of four vortex jumps. Arrows indicate the direction of vortex motion.  PDF

Movies of Vortex Dynamics

Physica C 408-410, 537 (2004)   PDF

moving flux quanta


Vortex entry
small size AVI, 250 Kb MPEG, 700 Kb QuickTime, 1.2 Mb
large size AVI, 650 Kb MPEG, 1.4 Mb QuickTime, 2.5 Mb

Initial vortex distribution is a result of cooling in a low magnetic field. Then, the applied field increases and new vortices slowly enter the crystal from the edge (located at the top). At larger fields the surface barrier is broken and many vortices penetrate very fast. Movie window: 25x35 microns, sample: NbSe2 crystal. PDF

Vortex entry with annihilation

small size AVI, 130 Kb MPEG, 700 Kb QuickTime, 1.0 Mb
large size AVI, 330 Kb MPEG, 1.1 Mb QuickTime, 3.3 Mb

Initial vortex distribution is a result of cooling in a low negative field (vortices are dark). Then, a positive field is applied, and the vortices exit the crystal slowly. When there is almost no vortices near the edge, the vortices of the opposite polarity (bright spots) enter the sample. Movie window: 25x25 microns, sample: NbSe2 crystal.

See also movies showing manipulation vortices with domain wall and difference movies

Comparison with other techniques

Principle of magneto-optical technique  

Existing methods for individual vortex visualization:

  • Bitter decoration
  • Scanning magnetic probes
  • Lorentz microscopy
  • Scanning tunneling microscopy

    to view more vortex images visit Gallery of Abrikosov Lattices

Advantages of MO imaging:

  • High temporal resolution
  • Applicability to any superconducting sample with a flat surface
  • Simplicity of imaging setup

Principle of MO-imaging

Maxima of the magnetic field from vortices in a superconducting sample (SC) give maxima in the Faraday rotation QF of incoming plane polarized light in a ferrite garnet layer (FGF) near the sample. Vortices appear as bright spots when imaged using a crossed polarizer(P)/analyser(A) setting. Details of the single-vortex imaging setup are given in  PDF

More about magneto-optics: MO imaging of Superconductors page.

Interaction between Individual Vortices and a Bloch Wall

Theory & Experiment for thick SC:  PDF (PRL-2007)

Theory for thick SC (non-charged wall):  PDF (PRB-2002)
Theory for thin SC (non-charged wall):  PDF (PRB-2002)


Domain wall in magneto-optical film

The domain wall can repel or attract vortices

Interaction between a Bloch wall in a ferrite-garnet film and a vortex in a superconductor is analyzed in the London approximation. Equilibrium distribution of vortices formed around the Bloch wall is calculated.

Our model can reproduce a counter-intuitive attraction observed between vortices and a Bloch wall having the opposite polarity. It is explained by magnetic charges appearing due to discontinuity of the in-plane magnetization across the wall.   PDF

MO images showing an enhanced vortex density around a Bloch wall

domain wall and vortices in superconductor
NbSe2. Zero-field cooling. Many vortices (white spots) are seen around two segments of a zigzag domain wall (black lines)		 flux quanta remain pinned
The domain wall has been removed		 flux quanta remain pinned
The vortex density across the wall obtained from the MO image (symbols) and the theoretical curve calculated within our model,   PDF


 

Manipulating flux quanta in superconductor with a Bloch wall Manipulation of vortices using a Bloch wall

Appl. Phys. Lett. 82, 79 (2003)   PDF

A moving wall can grab vortices. Depending on the ratio between the interaction and the pinning force, the wall can serve as vortex comb (vortices get tilted) or vortex shovel (vortices get depinned). On the images and movie below, a sweep of the wall creates a vortex-free gap at the turning point.  PDF

Tunable and movable nanomagnets can serve as vortex manipulators.

vortex lattice after field-cooling
Low-field cooling		 manipulating vortices with domain wall
After the wall has been moved in, and then out.		 Movie of a domain wall pushing vortices Movie of the domain wall pushing vortices

MPEG movie (1Mb)
AVI movie, DivX coding (2Mb)

 

Domain Wall Tip for Manipulation of Magnetic Particles Domain Wall Tip for Manipulation of Magnetic Particles

Phys Rev Lett. 91 208302 (2003)   PDF

We demonstrate a method for manipulation of single magnetic microparticles based on a domain wall tip displaced in a controlled manner. By applying an external magnetic field, the tip can either drag or push magnetic particles. This kind of tweezers has potential applications in probing and manipulating colloidal systems.

Superconductivity Lab @ University of Oslo