While international research into the theoretical particle that behaves as a magnetic monopole has not yet been successful, two researchers from the University of Liege have created these magnetic monopoles in their laboratory! Following the example of a group of researchers who announced the discovery of such quasiparticles in complex materials at very low temperatures, the researchers from Liege proved that it was possible to create magnetic monopoles by using small magnetized beads which can be bought on the internet for just a few Euros…This has caused a shake-up in the world of physics and has raised a number of questions.

The office of Professor Nicolas Vandewalle, director of GRASP (Group for Research and Applications in Statistical Physics of the University of Liege) has been inundated with magnetized beads. Magnetized beads made of neodymium which is a rare earth metal, were used in the past for flint lighters due to the fact that they are very malleable at room temperature. However, it has been known for some time that neodymium, which is alloyed with iron and boron (Nd₂Fe₁₄B), is an extremely powerful magnet and is also a very addictive toy! It only takes one click online to buy several hundred of these spheres and create astonishing structures. “Very few physicists have shown any interest in these spheres believing them to be a mere toy”, states Nicolas Vandewalle. “Yet at the start of this current year, 2014, three major scientific articles about the spheres carried out by separate groups have already been published. A group from Cambridge has studied the elastic properties of the chains formed by these beads and a group from France has studied the formation of rings. These studies have been carried out because there are more and more materials based on colloids, micrometric particles that can now be magnetized and therefore manipulated by magnetic fields. Colloids are sometimes introduced into living cells which makes it possible to control bacteria! These colloids also form chain and ring-shaped structures etc. The advantage is that the magnetic spheres are macroscopic and inexpensive while colloids cost a fortune! It therefore makes a lot more sense to study these phenomena by using neodymium bead magnets! Last but not least, our very own study has been conducted here in Liege (1)”.

Chains, rings and frustration !

More than a year has passed since Nicolas Vandewalle began to play with these small magnets himself. However, he has done so in way that only an experienced physicist might, by constantly seeking to understand the reasons behind the effects produced during his observations. There was a surprise in store right from the outset. When the small spherical beads are aligned, they form a chain (photo a). In this case, the dipole that constitutes each of the spherical beads is aligned.However, when the chain is folded, it unfolds itself and tends to return to its initial shape: the dipoles are disturbed and try to return to their point of balance. 

Surprisingly, the chain can be bent into a ring. In order to do this a certain amount of force must be applied until the ring suddenly forms.  In physics, this means that a potential barrier has been overcome! The barrier is overcome when the closing angle is in the vicinity of 280°.  “You would expect it to be the case that the longer the chain, the greater the angle at which the chain will close and stretch to 360° for an infinite chain. However, this was not observed, the angle at which the chain closes is around 280°, therefore , for a very long chain, the interaction between the first and last bead is not responsible for closing the chain. But why should this be so? It remains a mystery”, explains Nicolas Vandewalle.

(1) Magnetic ghosts and monopoles. N. Vandewalle and S. Dorbolo 2014 New J. Phys. 16 013050