Question 1

Is a higher N number always better for a neodymium magnet?

Accepted Answer

No. A higher number means more strength for the same size, but the very high-energy grades are rated for lower temperatures: one producer lists N35 to N48 at 80 °C, but N50 and N52 at 70 °C. Choose the lowest grade that gives the force you need with a reserve, then spend the margin on temperature and coating.

Question 2

What do the letters M, H, SH, UH, EH and AH mean?

Accepted Answer

They show intrinsic coercivity, that is, how strongly the material resists demagnetisation. One producer’s reference maximum temperatures are 80 °C for standard grades, 100 °C for M, 120 °C for H, 150 °C for SH, 180 °C for UH, 200 °C for EH and 220 °C for AH. These are reference values, not guarantees, and depend on the circuit the magnet works in.

Question 3

Why does a thin magnet lose strength at a lower temperature than a tall one?

Accepted Answer

A thin magnet in open air has a low working point on its demagnetisation curve, so it reaches the knee, where permanent loss begins, at a lower temperature. K&J Magnetics gives an N42 disc 1/2 in in diameter and 1/8 in thick that reaches the knee at 80 °C, while a tall N42 cylinder showed no losses until above 140 °C. For a thin magnet in open air, move up at least one suffix.

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