"We always look downeodymium magnets," laughed Laura Lewis, who developed a new type of magnetic material at Northwestern University in Boston. "People always think, 'Yes, yes, even in the refrigerator. Use magnets, how big a thing! ' "
In the eyes of Lewis, the story of the magnet is completely different. Permanent magnets are far more than just the key components of a refrigerator, or the piles of metal that can not be fiddled with in a middle school experiment. These metal pieces, which themselves produce a magnetic field, are in fact the core of many of the technologies supporting our modern life .
These technologies include personal items ranging from smartphones to headphones, thanks to the latest generation of high-performance magnets for internal use. But the magnet's influence is much greater than this, "Our world is running on the energy: cars, turbines, computers, satellites, and all kinds of transportation," Rochester, New York, Arnold magnetic technology company Stephen Kang "They all need magnets," explains Steve Constantinides.
And now, a crisis is emerging. By the global appetite for the stimulation of gluttonous energy, the demand for the best quality magnet is converging into an undercurrent of the flood. The trouble is, we do not know where to get so many magnets. Suddenly, Konstantinides, Lewis and their colleagues discovered that their work was receiving unprecedented attention.
It is not easy to make a good magnet. In the 19th century, classical electromagnetism theory tells us that the movement of the charge will produce a magnetic field, the natural magnet magnetic field, in turn, can drive the charge. This discovery is enough to make a large number of iron, the most common magnetic material in nature, the core of such critical power technologies as motors, generators and transformers. The cores store energy in these devices, converting mechanical power and current into each other until today in this way.
But to explain how permanent magnets have the ability to generate magnetic fields and interact with the magnetic field, you have to use a lot of 20th century physics Caixing. All of this comes from the behavior of the electrons in the atoms in the solid. Applying quantum theory and Einstein's relativistic principles to these electrons, you will find that they behave like small rods pointing either up or down, depending on the spin value of the electron.
In most substances, the number of electrons pointed to each half, so the whole does not show the magnetic effect. But for some elements, such as iron, and its neighbors on the periodic table – cobalt and nickel, if the outermost layers of all the atoms, the electrons involved in chemical bond formation, are parallel to each other, The overall energy will be reduced. As long as these electrons are firmly fixed in a solid lattice where they can be freely flipped, and then a little magnetic field is applied, the solids formed by these elements are able to generate their own magnetic field and remain unanimously maintained. In this way, you get a permanent magnet.
Quality permanent magnets
Yes, this is a permanent magnet, but this is a good magnet it? "I have a high-quality magnet to meet the requirements of the list," said Constantinides, "to expand can be very long." Modern iron-based or ferrite magnets, inexpensive and rich in raw materials have a hook , Their relative magnetic strength is strong enough, and corrosion resistance also come out on top, but they have a fatal drawback: the energy density is too low. This means that if you want a strong magnetic field, you have to use a terrible pile of ferrite magnets made of a giant. "The ferrite magnets are big and heavy iron pieces," Lewis added.
