`Sony Walkman and neodymium-iron-boron magnets`

The 50× volume reduction from Alnico to NdFeB explains why portable battery-powered audio became practical.

What does it mean? If I look at the old Alnico magnets from the 1930s, in order to have a certain magnetization — this is a thousand gauss at five millimeters from the pole face — you have to have eleven, twelve cubic centimeters of Alnico. Alnico 9 is a little better. You get up to neodymium iron boron — you never see them as big fat long magnets, because you don't need it geometrically. You have a drop of a factor of 50 or so in volume. So now all of your motors and things like that — when the Sony Walkman first came out in the 1980s, he had changed the batteries about every two or three hours. Now who would listen to an MP3 player if the battery lasted two or three hours? You get lots of time out of these things now.

~15 lb of NdFeB magnets per modern car; starter motor shrunk from 30 lb to fist-sized. Discovered ~1980 at GM Research Lab. Connects to the rare earth embargo case (§5.p9).

Basically it's B squared. Steels before the 1920s, alnico magnets in the 1930s, rare earth cobalt — this is samarium cobalt in the 1960s. It was the early 70s — here's samarium cobalt, iron, nickel, copper. That's about the time that I went to General Electric, and this stuff had a BH product of over 30 compared to the old aluminum-nickel-cobalt alloys, which you had on your little Etch-a-Sketch — remember the iron filings, and you put the beard on the man and mustache. That's the alnico magnets. They're not very strong. Then about 1980, General Motors Research Lab discovered neodymium-iron-boron, which is that little thing. Now they're all over the place.