Over the last few decades, cloaking devices have come closer and closer to becoming reality. Scientists have masked objects from the human eye using various metamaterials. They've created sonic invisibility barriers. They've even masked heat. And now they may be able to cloak a magnetic field, too.
Ships cruising along during war time are sometimes sunk by mines that don't strike them directly, but sense their magnetic field and detonate. Patients in an MRI machine are subjected to enormous magnetic fields, which is problematic if they have any metal implants like pacemakers. So far, stifling a magnetic field has seemed impossible, until a group of scientists at the Universitat Autònoma de Barcelona designed an 'antimagnet'.
The antimagnet has been described as a cloaking device for magnetic fields, and in fact might consist of an actual cloak. Like a cloak it can conform to the shape of the object and like a cloak it has several layers. Closest to the object emitting the magnetic field would be a layer of superconducting material. Superconductors, materials that when dropped below a certain temperature conduct electricity with no resistance, have been shown to repel magnetic fields. There are many pictures of magnets hovering above superconductors, held up and away from the material. The superconductor blocks the effects of the magnet.
The problem is, it blocks them from both sides. Magnets outside the cloak would feel the 'push' as their own fields were blocked. The only solution is to line the other side of the magnetic invisibility cloak with metamaterials. Each metamaterial would have a different permeability to magnetic fields, building the illusion that the outside magnetic field was penetrating the inside of the cloak.
The overall impression would be of a blank stretch of space, covering the magnetic field inside and letting it pass by undetected.
Image: Julien Bobroff, Frederic Bouquet, Jeffrey Quilliam, LPS, Orsay, France
Via the New Journal of Physics.