Our mighty 4mm cubic rare earth magnets are incredibly useful, mesmerizing to fiddle with, and a steal for only 5 bucks for a tube of 20.
We had these custom manufactured to the highest magnetization the factory could concentrate into the small space.
Made from a neodymium (Nd) alloy, these magnets each have about a 4lb pull (direct metal-to-metal contact). They are nickel coated since the magnetic material is a highly compressed powder.
*NOT A TOY. NOT FOR YOUNG CHILDREN. DO NOT SWALLOW*
Only a few elements are naturally magnetic at room temperature. Neodymium is not one of these elements; however, in the 1980s, General Motors found that an alloy of neodymium, iron, and boron (Nd2Fe14B) not only produces a magnet, but its crystal structure causes it to be an especially strong magnet.
Also called “rare-earth” magnets since neodymium is in the group of elements called rare-earths.
A neodymium magnet (also known as NdFeB, NIB or Neo magnet) is the most widely used type of rare-earth magnet. It is a permanent magnet made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. Developed independently in 1984 by General Motors and Sumitomo Special Metals, neodymium magnets are the strongest type of permanent magnet available commercially. Because of different manufacturing processes, they are divided into two subcategories, namely sintered NdFeB magnets and bonded NdFeB magnets. They have replaced other types of magnets in many applications in modern products that require strong permanent magnets, such as electric motors in cordless tools, hard disk drives and magnetic fasteners.
Neodymium is a metal which is ferromagnetic (more specifically it shows antiferromagnetic properties), meaning that like iron it can be magnetized to become a magnet, but its Curie temperature (the temperature above which its ferromagnetism disappears) is 19 K (−254.2 °C; −425.5 °F), so in pure form its magnetism only appears at extremely low temperatures. However, compounds of neodymium with transition metals such as iron can have Curie temperatures well above room temperature, and these are used to make neodymium magnets.
The strength of neodymium magnets is the result of several factors. The most important is that the tetragonal Nd2Fe14B crystal structure has exceptionally high uniaxial magnetocrystalline anisotropy (HA ≈ 7 T – magnetic field strength H in units of A/m versus magnetic moment in A·m2). This means a crystal of the material preferentially magnetizes along a specific crystal axis but is very difficult to magnetize in other directions. Like other magnets, the neodymium magnet alloy is composed of microcrystalline grains which are aligned in a powerful magnetic field during manufacture so their magnetic axes all point in the same direction. The resistance of the crystal lattice to turning its direction of magnetization gives the compound a very high coercivity, or resistance to being demagnetized.
The neodymium atom can have a large magnetic dipole moment because it has 4 unpaired electrons in its electron structure as opposed to (on average) 3 in iron. In a magnet it is the unpaired electrons, aligned so they spin in the same direction, which generate the magnetic field. This gives the Nd2Fe14B compound a high saturation magnetization (Js ≈ 1.6 T or 16 kG) and a remnant magnetization of typically 1.3 teslas. Therefore, as the maximum energy density is proportional to Js2, this magnetic phase has the potential for storing large amounts of magnetic energy (BHmax ≈ 512 kJ/m3 or 64 MG·Oe). This magnetic energy value is about 18 times greater than "ordinary" ferrite magnets by volume and 12 times by mass. This magnetic energy property is higher in NdFeB alloys than in samarium cobalt (SmCo) magnets, which were the first type of rare-earth magnet to be commercialized. In practice, the magnetic properties of neodymium magnets depend on the alloy composition, microstructure, and manufacturing technique employed.
The Nd2Fe14B crystal structure can be described as alternating layers of iron atoms and a neodymium-boron compound. The diamagnetic boron atoms do not contribute directly to the magnetism but improve cohesion by strong covalent bonding. The relatively low rare earth content (12% by volume) and the relative abundance of neodymium and iron compared with samarium and cobalt makes neodymium magnets lower in price than samarium-cobalt magnets.
Just what I was looking for. These are nice strong little magnets. Came promptly. Love this shop!
This is a neat set of neodymium magnets that I have on my desk at work, they are a minor conversation starter but are also great for implanting inside 3D prints.