Magnetic Component Engineering

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Stabilization and Calibration


Stabilization is the deliberate treatment of a magnet by magnetic, thermal, physical, or other controlled external demagnetizing influences so as to preclude or minimize the future change in magnetic performance of a magnet in the field during use.

Calibration is the deliberate treatment of a magnet by magnetic, thermal, physical, or other means to reduce the level of magnetization to a precise, predetermined level, thereby achieving a tighter tolerance on the magnetic performance.

What is the difference between the two?

Stabilization is used to prevent the magnet from permanently changing in its working environment. A stabilized magnet will act predictably in its environment. For example, when a magnet is heated to say 250C, it would see two types of losses:

  1. Reversible Losses
  2. Irreversible losses

Reversible Losses are those that come back when the magnet is cooled to room temperature. Irreversible losses dont come back; they are permanently lost. In our example, let us assume we were using S2669 Samarium Cobalt. Its reversible loss is (-0.03%/C). At 250C (assume room temperature is 20C), its reversible loss = (250-20) x (-0.03%) = -6.9%. The irreversible losses are a function of design. For this example let us assume it is 4%. Therefore the total loss = (6.9+4.0)% = 10.9% at 250C. Now let us cool the magnet back to 20C. Only 6.9% was recoverable. The 4% was not recoverable. The magnet will have returned to 96% of its original value.

If this magnet had been stabilized, the 4% would have been lost during stabilizing; therefore, subsequent changes in temperature to 250C would lead to only the 6.9% loss at the elevated temperature. When cooling back to 20C, the 6.9% will recover. Word of caution The magnets MUST BE SATURATED prior to stabilization! This ensures that the "weak" domains are eliminated.

Calibration is used to control the magnetic tolerance to tighter tolerances than the manufacturing process of the base material can yield. In this example, assume a batch of magnets made from S2669 is guaranteed to have a total flux within a 5% band. But let us assume an application that requires these magnets to be within a 1% band. This batch would have to be processed as follows:

  1. The nominal value would be calculated, or a required value would be determined.
  2. The magnets that exhibit a flux density or total flux ABOVE this required value would be demagnetized to bring them within 1%.
  3. Magnets that are lower than the required value would be rejected from the batch. Lot control, controlled demagnetizing, statistical analysis and statistical processing achieve calibration. Magnetic Component Engineering offers this service to customers with demanding applications. Word of caution The magnets MUST BE SATURATED prior to calibration!

In both scenarios, the function of FIRST SATURATING the magnet cannot be emphasized enough! If the magnets were not saturated prior to stabilization or calibration, the magnets would be considered "unstable" and erratic results would be observed in the application. Magnetic Component Engineering offers both services. If you require stabilization or calibration, discuss this with our engineers. We can also help you determine and write the specifications.