question: How are magnets made into different shapes if they lose magnetism on impact or heating?
comment: Rare earth magnets are made by creating a fine powder, pouring it into a mold, and applying a strong magnetic field to rotate all the magnetic grains so they're parallel. Then the aligned powder is compacted and sintered. Sintering means the magnet is heated enough to fuse the corners of the grains to each other, but not so much that it reaches the Curie point. URL_0
passages: A "magnetically induced deformation" of about 0.2% was presented in 1996 by Dr. Kari Ullakko and co-workers at MIT. Since then, improvements on the production process and on the subsequent treatment of the alloys have led to deformations of up to 6% for commercially available "single crystalline" Ni-Mn-Ga MSM elements, as well as up to 10-12 % and 20% for new alloys in R&D stage.
   Injection-molded magnets are a composite of various types of resin and magnetic powders, allowing parts of complex shapes to be manufactured by injection molding. The physical and magnetic properties of the product depend on the raw materials, but are generally lower in magnetic strength and resemble plastics in their physical properties.
   Section::::Types of permanent magnets.:Composites.
  
  Ceramic, or ferrite, magnets are made of a sintered composite of powdered iron oxide and barium/strontium carbonate ceramic. Given the low cost of the materials and manufacturing methods, inexpensive magnets (or non-magnetized ferromagnetic cores, for use in electronic components such as portable AM radio antennas) of various shapes can be easily mass-produced. The resulting magnets are non-corroding but brittle and must be treated like other ceramics.
   BULLET::::- Heating the object higher than its Curie temperature, allowing it to cool in a magnetic field and hammering it as it cools. This is the most effective method and is similar to the industrial processes used to create permanent magnets.
   Section::::Types.:Magnetorheological finishing.:Applications.
  
  Sub-nanometer scale polishing
  
  BULLET::::- Freeform nonmagnetic workpieces
  
  Section::::Types.:Magnetic fluid finishing.
   BULLET::::- In process industries, powerful neodymium magnets are used to catch foreign bodies and protect product and processes
  
  Neodymium content is estimated to be 31% of magnet weight
  
  Section::::Applications.:New applications.
   BULLET::::- Some demagnetization or reverse magnetization will occur if any part of the magnet is subjected to a reverse field above the magnetic material's coercivity.
  
  BULLET::::- Demagnetization progressively occurs if the magnet is subjected to cyclic fields sufficient to move the magnet away from the linear part on the second quadrant of the B-H curve of the magnetic material (the demagnetization curve).
  
  BULLET::::- Hammering or jarring: mechanical disturbance tends to randomize the magnetic domains and reduce magnetization of an object, but may cause unacceptable damage.
  
  Section::::Types of permanent magnets.
  
  Section::::Types of permanent magnets.:Magnetic metallic elements.
   A special coil is placed near the metallic workpiece, replacing the pusher in traditional forming. When the system releases its intense magnetic pulse , the coil generates a magnetic field which in turn accelerates the workpiece to hyper speed and onto the die.
  
  The magnetic pulse and the extreme deformation speed transforms the metal into a visco-plastic state – increasing formability without affecting the native strength of the material. See the magnetic pulse forming illustration for a visualization.
   BULLET::::- MQU are the highest-performing isotropic powders to be used in the production of MQ2-type magnets, which are fully dense isotropic magnets.
  
  Section::::Production.
  
  Nd-Fe-B powder is bound in a matrix of a thermoplastic polymer to form the magnets. 
   General Motors (GM) and Sumitomo Special Metals independently discovered the NdFeB compound almost simultaneously in 1984. The research was initially driven by the high raw materials cost of SmCo permanent magnets, which had been developed earlier. GM focused on the development of melt-spun nanocrystalline NdFeB magnets, while Sumitomo developed full-density sintered NdFeB magnets.
  
  GM commercialized its inventions of isotropic Neo powder, bonded neo magnets, and the related production processes by founding Magnequench in 1986 (Magnequench has since become part of Neo Materials Technology, Inc., which later merged into Molycorp). The company supplied melt-spun NdFeB powder to bonded magnet manufacturers.
   The mechanism by which molecule-based magnets stabilize and display a net magnetic moment is different than that present in traditional metal- and ceramic-based magnets. For metallic magnets, the unpaired electrons align through quantum mechanical effects (termed exchange) by virtue of the way in which the electrons fill the orbitals of the conductive band. For most oxide-based ceramic magnets, the unpaired electrons on the metal centers align via the intervening diamagnetic bridging oxide (termed superexchange). The magnetic moment in molecule-based magnets is typically stabilized by one or more of three main mechanisms:
  
  BULLET::::- Through space or dipolar coupling
   As earlier discussed, MEMS devices are designed and fabricated using special micro-fabrication techniques. The major challenge however for magnetic MEMS is the integration of the magnet into the MEMS device. Recent research has suggested solutions to this challenge.
  
  Section::::Integrating the magnet into the MEMS device.:Fabrication (or molding) of the magnet.
  
  There are several ways by which the magnet could be fabricated on a MEMS structure:
  
  BULLET::::- Sputtering: Argon ion bombardment of the material release particles of the material. Mainly for depositing rare earth magnets. Deposition rate and film surface area depend on sputtering tool and target size
   In some cases, the mixture of finely-powdered precursors is pressed into a mold. For barium and strontium ferrites, these metals typically supplied as their carbonates, BaCO or SrCO. During the heating process, these carbonates undergo calcination:
  
  After this step, the two oxides combine to give the ferrite. The resulting mixture of oxides undergoes sintering.
  
  Section::::Production.:Processing.
   BULLET::::- Vacuum induction melting (VIM): This is done by using alternating magnetic fields to heat the raw materials in a crucible (generally carbon). This is also done in a high vacuum.
   For permanent magnets this is usually only a small change, but if you have an electromagnet that consists of a wire wound round an iron core, and you bring a permanent magnet near to that core, then the magnetization of that core can change drastically (for example, if there is no current in the wire, the electromagnet would not be magnetic, but when the permanent magnet is brought near, the core of the electromagnet becomes magnetic).
   BULLET::::- Magnets can be used in scrap and salvage operations to separate magnetic metals (iron, cobalt, and nickel) from non-magnetic metals (aluminum, non-ferrous alloys, etc.). The same idea can be used in the so-called "magnet test", in which an auto body is inspected with a magnet to detect areas repaired using fiberglass or plastic putty.
   BULLET::::- Operating temperatures between -40 and 60 °C
  
  BULLET::::- Change in magnetic permeability and electric resistivity during deformation
  
  Section::::Development of the alloys.
   Inverse GMR is also observed if NiCr alloy is replaced by vanadium-doped nickel, but not for doping of nickel with iron, cobalt, manganese, gold or copper.
  
  Section::::Device preparation.:Types of GMR.:GMR in granular structures.
   The magnetic shape memory effect occurs in the low temperature martensite phase of the alloy, where the elementary cells composing the alloy have tetragonal geometry. If the temperature is increased beyond the martensite–austenite transformation temperature, the alloy goes to the austenite phase where the elementary cells have cubic geometry. With such geometry the magnetic shape memory effect is lost.
  
  The transition from martensite to austenite produces force and deformation. Therefore, MSM alloys can be also activated thermally, like thermal shape memory alloys (see, for instance, Nickel-Titanium (Ni-Ti) alloys).
  
  Section::::The magnetic shape memory effect.
   BULLET::::2. a negative value of the anisotropy of the zero field splitting ("D")
  
  Most SMMs contain manganese but can also be found with vanadium, iron, nickel and cobalt clusters. More recently, it has been found that some chain systems can also display a magnetization that persists for long times at higher temperatures. These systems have been called single-chain magnets.
  
  Section::::Types of permanent magnets.:Nano-structured magnets.
  
  Some nano-structured materials exhibit energy waves, called magnons, that coalesce into a common ground state in the manner of a Bose–Einstein condensate.
  
  Section::::Types of permanent magnets.:Rare-earth-free permanent magnets.
   Bonded neo magnets were first invented in 1982, and since that time they have been refined to a point where they now possess the highest magnetic strength of the four types of permanent magnets.
  
  Section::::Applications of bonded neo powder.
   Having obtained the ferrite, the cooled product is milled to particles smaller than 2 µm, sufficiently small that each particle consists of a single magnetic domain. Next the powder is pressed into a shape, dried, and re-sintered. The shaping may be performed in an external magnetic field, in order to achieve a preferred orientation of the particles (anisotropy).
   An electromagnet is made from a coil of wire that acts as a magnet when an electric current passes through it but stops being a magnet when the current stops. Often, the coil is wrapped around a core of "soft" ferromagnetic material such as mild steel, which greatly enhances the magnetic field produced by the coil.
  
  Section::::Discovery and development.
   Magnetization reversal, also known as switching, refers to the process that leads to a 180° (arc) re-orientation of the magnetization vector with respect to its initial direction, from one stable orientation to the opposite one. Technologically, this is one of the most important processes in magnetism that is linked to the magnetic data storage process such as used in modern hard disk drives. As it is known today, there are only a few possible ways to reverse the magnetization of a metallic magnet:
  
  BULLET::::1. an applied magnetic field
  
  BULLET::::2. spin injection via a beam of particles with spin
   Industrial MHD problems can be modeled using the open-source software EOF-Library. Two simulation examples are 3D MHD with a free surface for electromagnetic levitation melting, and liquid metal stirring by rotating permanent magnets.
  
  Section::::Applications.:Magnetic drug targeting.
  
raw_presuppositions: Magnets are made into different shapes in their working state.
raw_corrections: Rare earth magnets are ground into a powder and shaped in a mold.