Magnet strength - storage

Some time last year I discovered my old magnets from childhood. They were in an old Sucrets metal box, clinging together. All small magnets of various sizes and shapes. All seemed to still have their strength after these 45-50 years. Whee.

Expect someday I'll order some of those "rare earth" magnets off of Ebay to play with. I wonder what those magnets do to the postal sorting machines?

A soft material is easily magnetized and easily demagnetized. You want soft materials (carbon steel) for electromagnets (so they let go when the juice is turned off), and hard materials for permanent magnets. Alnico 5 and 8 were the preferred materials that showed a willingness to accept magnetism and reluctance to give it up. But now we have ceramic magnet materials (Samariam Cobalt is popular) that do not display one undesirable trait of the previous materials. It does not demagnetize by beating on it nor placing metallic objects on it and pulling them off. Additionally, it can accept more magnetism (gauss) in a given dimension so they are smaller for a given gauss level....not cheaper.

Microwave power tubes (like ones used in wideband cell phone towers) have gone to using these ceramics as the preferred material.

txblu

For ceramic magnets, I don't have a clue.

For what it is worth.

Roger