The magnetic domains are locked in position as established by initial magnetization. The domains are held in place until acted upon by forces exceeding the locked in force. Various factors affecting magnet stability include metallurgical changes, time, temperature, reluctance changes, adverse fields, shock, stress and vibration as quoted from Indiana General.

Metallurgical: In the older magnets such as cobalt, tungsten or chromium-steels, metallurgical changes may take place at or near room temperature as a function of time. It is important to note that metallurgical changes do not take place in any measurable degree at room temperature in the newer permanent magnets such as Alnico or Ceramic. IG

Time: Time versus flux records made by precise lab measurements, under carefully controlled conditions have shown that a newly magnetized magnet will lose a minor percent of its flux as a function of “age”. IG

Temperature:

1. Metallurgical changes occur in magnets exposed to very high temperatures. Such flux changes are not recoverable by remagnetization.

2. Irreversible losses: are defined as partial demagnetization of the magnet from exposure to high or low temperatures. These losses are recoverable by remagnetization. 3. Reversible changes are positive or negative flux changes which are recovered when the magnet returns to the initial temperature. IG

Reluctance: changes many occur if a magnet is magnetized in a circuit and subsequently subjected to permeance changes (such as a air gap or opening in a circuit of a magnet). IG

Others: Contacting the magnet with ferro-magnetic materials such as screw drivers or other metal objects at points other than the poles can drop the flux at the poles. Keep other magnetic objects away from magnets. Shipping magnets in close proximity to each other can change the flux in a magnet. Proper equipment must be used to properly magnetize the magnet to its maximum strength. The magnets should be shipped in a proper North – South relationship. IG

Adverse Fields: Adverse fields may partially demagnetize a magnet, depending upon the material properties and the intensity and direction of the field. IG

Shock: Shock, stress and vibration on most permanent magnet materials are very minor. Dropping a magnet on a metal surface can reduce the flux in the magnet.

Flux loss In newly Magnetized Permanent Magnets.
Magnet Material Loss per log cycle (11.4 yrs.) Loss at 100,00 hrs
Ceramic negligible negligible
Alnico 3 (near max. energy) 0.4% 2.4%
Alnico 3 (near coercive) 0.6% 3.6%
Alnico 5 (near residual) 0.01% 0.06%
Alnico 5 (near max. energy) 0.15% 0.9%
Alnico 5 (near coercive) 0.4% 2.4%
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