Maglev Experiment

Diamagnetic Effect

Xu Ru is a PhD candidate at Polytechhnique School of Montreal

Xu Ru is a PhD candidate at Polytechhnique School of Montreal

By Xu Ru

When Geim was working in Nijmegen, the main advantage in the lab was the powerful electromagnets, but meanwhile it rendered him headache: although those magnets could generate magnetic field of 20 Tesla, a little bit stronger than many of peer competitors (superconducting magnetic field approximately 16 to 18 Tesla), but these behemoths costed so much charge electricity that every evening they only spent a few hours on them when the electricity was cheap. For research in mesoscopic superconductivity they only needed very weak magnetic field (less than 0.01 Tesla), so he could not use these electromagnets. This made him feel guilty as a High Magnetic Field Laboratory researcher. He had a sense of responsibility to find something that he could use to do research with these powerful electromagnets. He realized that compared to other superconducting magnet, the only obvious advantage of these electromagnets was that they could be operated at room temperature rather than being cooled down to the temperature of liquid helium like other superconducting magnets. However, this did not seem an advantage for ordinary people, because most of the condensed matter experiments required very low temperature environment. 

Finally, he accidentally learned a so-called "magnetized water" phenomenon. Allegedly, a permanent magnet placed on the hot water tap could prevent scale formation in pipes inside. Or if we put a magnet on the faucet, it would not form a thick layer of sediment inside the kettle. Those magnets were everywhere, readily available. There were hundreds of articles describing this phenomenon on the Internet, but the physical principles behind it were not clear, and even many researchers did not believe the existence of this phenomenon. However, the strong magnetic field at room temperature made him come up with the idea of magnetization of water experiments. He thought if magnetized water effect really existed, 20 Tesla magnetic field should produce much more pronounced effect than the 0.1 Tesla ordinary permanent magnet.

With this in mind, on a Friday evening, he poured a little water into the instrument inside the strong magnetic field. Slopping into the experimental apparatus was clearly not a formal experiment operation. Obviously, no one had ever tried to do this kind of silly thing, although similar instruments in several laboratories around the world had existed for decades. To his surprise, the water stayed in the center of the magnet instead of flowing out. Access student Humberto Carmona from Nottingham and Geim had fun there for more than an hour. They stirred the water in the center with a stick, varying the intensity of the magnetic field. Finally, they saw the amazing phenomenon as shown in FIG. 1, a water polo suspended in the air!

Figure 1

Figure 1

This was amazing! They soon realized that behind this phenomenon it was the familiar diamagnetic properties. However, it took him a long time to ensure himself that such weak diamagnetic effect of the water (in the magnetic field B, water generates a magnetic field 0.00001 * B to resist it). it was billions of times weaker than the magnetic iron, the water was able to resist gravity. Many of his colleagues, including researchers who dealt with strong magnetic field, thought that this was a hoax.

They tried many objects for suspension, and the suspension of frog (Figure 2) attracted widespread media attention, even was written into many physics textbooks. Although it was somewhat bizarre, this experiment let people re-examine the diamagnetic effect— they no longer thought it was just a trivial property of the materials.

Figure 2

Figure 2