But the most interesting was yet to come… Nicolas Vandewalle then began to use bigger and bigger chains. It became easier and easier to create rings because the chains were therefore more and more flexible and folded in on themselves more easily.  From this, it was possible to form a “droplet” which was an even more interesting structure because a kind of junction was created (photo b). If the droplet is broken at the point of the triple junction, a ghost function remains (photo c) which represents an angle of around 80°. This ghost junction is permanent, the system always returns to this configuration! “This is very disturbing”, explains Nicolas Vandewalle. “I studied the orientation of the small dipoles. They were all aligned in accordance with the chain but there was a defect concerning the bead that was located in the center. In magnetism, this is known as a frustration. In a manner of speaking, this bead cannot know how it is oriented and in what direction it should align itself”.

Magnetic monopole

Such defects have been the subject of studies for a long time now, notably by P.W. Anderson (Nobel prize for physics in 1977) in the 1950s. He predicted that in certain materials, these frustrations could play an important role. But it was only as recently as 2008 and 2009, that materials known as “spin ice” were studied, because they have the same crystallographic structure as ice , but are formed by a stacking of small magnets (on an atomic scale, these are called spins, hence the name). This formed the basis of Nicolas Vandewalle’s question: “Could there be a connection between the magnetized beads and these microscopic materials that are difficult to study and which physicists have attempted to observe at very low temperatures with equipment that most teams cannot afford”? What exactly was discovered by those who study this type of material?  That they behave just like a magnetic monopole!