What is the Difference between N35 and N52 Magnets?

What are N35 and N52 magnets? Seen from their grade strings, both of them are sintered neodymium iron boron (NdFeB) magnets. These two magnets have the same intrinsic coercivity Hcj level higher than 12 kOe (in CGS unit) or 955 kA/m (in SI unit). It is also obviously seen that their maximum energy product (BH)max are around 35 and 52 MGOe, respectively. This huge difference means that the N52 magnets have around 49% more energy than that of the N35 magnets. In other words, a motor or device using N52 magnet(s) would have much higher performance than that using N35 magnet(s), and/or it would be much smaller and lighter.

neodymium iron boron, NdFeB magnets, N35 and N52 Demagnetization Curves

As N35 and N52 magnets both are sintered NdFeB magnets, why do they have so huge difference in (BH)max? Is it a quality issue? The answer is absolutely not. It should be noted that the grade classification of permanent magnets is only based on their magnetic properties, it has nothing to do with quality. A specific grade is a macro performance resulting from material composition and microstructure. In order to achieve a required grade or relative magnetic properties, it can be manipulated and controlled via material ingredients and production process.

Although N52 magnets have extremely high (BH)max at room temperature, currently the top level among commercial magnets, they are used in a few applications due to their high cost (around 50% higher than that of N35 magnets). Actually N35 magnets are the most widely used in various applications among sintered NdFeB magnets. Compared with other permanent magnets such ceramic/ferrite magnets, typical (BH)max around 4 MGOe, N35 magnets have nearly 8-9 times stronger power. In some cases, it really needs NdFeB magnets with higher (BH)max, N45, N48 and N50 magnets are already strong enough. Via structure design and optimization, using these grade magnets instead of N52 magnets are able to meet target performances at lower costs.

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