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| Intro to Magnetism: Classification of Materials |
| Types of Materials |
Examples |
Characteristics |
| Nonmagnetic |
sulfur,copper,diamond,zinc, aluminum |
domains do not form; although electron spins create magnetic fields, they cancel out. |
| Ferromagnetic |
iron(Fe),cobalt(Co,nickel(Ni),neodymium(Nd), samarium(Sm) |
domains form as electron spin are aligned, but the domains themselves are scrambled until they're placed in a magnetic field. |
| Permanent Magnets |
lodestone,compass needle,horseshoe magnet, the earth's core |
domains are locked into place by impurities |
| Types of Permanent magnets |
Composition (ferromagnetic
elements in bold) |
Characteristics |
Relative Strength+ Permanence=Energy
Product (gauss-oersteds) |
| lodestone |
magnetite = iron oxide(Fe3O4)
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tough to demagnetize but
relatively weak |
<1 |
| alnico |
iron + aluminum+ nickel
+cobalt |
developed prior to WWII and
played an important role in development of radar and eventually
microwave ovens |
1.4-->4.5 |
| ferrrites |
iron oxide,
barium and strontium |
soft and cheap to produce; 75% of
magnets on market |
0.6 --> 3.6 |
| neo magnets |
iron + neodymium + boron |
allow for compact designs of
speakers and motors |
35-41 |
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sources: Livinggton, James D. The Force is With Us. Britannica
Science Annual. 1999 |
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