![]() ![]() A full understanding of how adding neodymium to iron makes a powerful permanent magnet, and how making a powerful magnet without any rare earth is possible, would require a deeper dive into crystallography than we have space for here. This is a fiendishly complicated subject, with nomenclature and terminology that’s confusing because it seems like it’s the same as standard chemical formula notation, but it’s clearly not. Going further down the rabbit hole of magnetism requires getting comfortable with the concepts of crystallography. Source: Jun Sugiyama, et al DOI: 10.1103/PhysRevMaterials.3.064402 If you can figure it out, good luck to you. The Power of Crystals Crystal structure of Fe 14Nd 2B. The most common rare-earth magnet alloy, a combination of iron, neodymium, and boron, has a Curie temperature in the range of 300-400☌, depending on the exact mix of elements. To get around that, rare-earth metals are mixed with other ferromagnetic elements to form alloys that have a strong magnetic coercivity while also having a decent Curie point. In fact, it would need to be chilled to below 20 K to have any magnetic properties. At room temperature, a pure bar of neodymium wouldn’t be a magnet at all. This is due to their relatively low Curie point, which is the temperature above which a substance loses its magnetic properties. ![]() Rare-earth metals like neodymium have very high magnetic anisotropy, which contributes to the strength of rare-earth magnets.īut rare-earth metals by themselves actually make pretty poor magnets, at least on a practical level. This is referred to as having a high magnetic anisotropy, and is one of the characteristics of strong magnets. Just like the electrons in an atom of a magnetic element have to not fight each other, the atoms must also arrange themselves so that their magnetic moments are all pointing the same way. Magnetism is about getting all those intrinsic magnetic moments lined up and acting in the same direction. There’s more to a magnet than just where its ingredients came from on the periodic table, though. But what about nitrogen, all the way over there in the p-block? Source: Minute Physics Ferromagnetic elements tend to have unpaired electrons, like those from the middle of the d- and f-blocks of the periodic table. These elements tend to come from two specific areas of the periodic table: the d-block metals like cobalt, nickel, and iron, and the f-block actinides lanthanides, which include the rare-earth metals like samarium, neodymium, and praseodymium. But in atoms with unpaired electrons in their outer shells, there’s nothing to cancel out the magnetic moments, which means these elements are magnetic. In atoms with filled electron shells, these magnetic moments cancel each other out because each pair of electrons have moments that point in opposite directions. We’ve taken a stab at the basics of magnetism before, but to summarize, any charged particle, like an electron, has what’s known as an intrinsic magnetic moment, meaning they act like little magnets. Even physicists eventually get to a point where their answer comes down to, “We just don’t know.” But that doesn’t mean magnetism is a complete mystery, and the things that we do know about it are pretty straightforward, and actually help in understanding how both rare earth magnets and their alternatives work. To start things off, what even is a permanent magnet? Like many simple questions about nature, there’s no easy answer that doesn’t require a fair amount of hand-waving. In fact, the only thing needed to make them is iron and nitrogen, plus an understanding of crystal structure and some engineering ingenuity. Luckily, there’s more than one way to make a magnet, and it may soon be possible to build permanent magnets as strong as neodymium magnets, but without any rare earth metals. What’s more, extracting them from their ores is a tricky business in an era of increased sensitivity to environmental considerations. It’s not that rare earth elements like neodymium are all that rare geologically rather, deposits are unevenly distributed, making it easy for the metals to become pawns in a neverending geopolitical chess game. ![]() These advances come at a cost, though, as the rare earth elements needed to make them are getting harder to come by. And that’s not to mention the motors in electric vehicles and the generators in wind turbines, along with countless medical, military, and scientific uses. The amount of magnetic energy packed into these tiny, shiny objects has led to technological leaps that weren’t possible before they came along, like the vibration motors in cell phones, or the tiny speakers in earbuds and hearing aids. Since their relatively recent appearance on the commercial scene, rare-earth magnets have made quite a splash in the public imagination. ![]()
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