Neodymium Magnets: A Comprehensive Guide to Properties, Manufacturing Process, Applications, and More - Your Ultimate Resource
Geometry of Neodymium Magnets
Neodymium magnets, also known as NdFeB magnets or neo magnets, are the third generation of rare earth magnet developed in early 1980s independently by General Motors and Sumitomo Special Metals. According to manufacturing process, they can be divided into sintered neodymium magnets, bonded neodymium magnets, and hot-pressed neodymium magnets. Sintered neodymium magnets have the highest energy product among all types of permanent magnets.
Tengye Magnetic is dedicated to the manufacture of sintered neodymium magnets in authentic grades according to customer requirements.
Grade of Neodymium Magnets
According to remanence (Br) and coercivity (Hc), the grade of sintered neodymium magnets can vary in two ways. Take N42UH grade as an example, N represents Neodymium, 42 remanence, and UH coercivity (resistance to demagnetization). Generally, magnet grade can range from N30 to N55 in the perspective of remanence, N to TH in the perspective of coercivity or resistance to demagnetization. There are a variety of neodymium magnet grades that are suitable for different application requirements.
Grade | Remanence (Br) | Intrinsic Coercivity (Hcj) | Coercivity (Hcb) | Maximum Energy Product (BH)max | Temperature Coeffcient (α) | Max.Working Temp. | ||||||||||
T | kGs | kA/m | kOe | kA/m | kOe | kJ/m3 | MGOe | αBr | αHcj | °C | ℉ | |||||
Max | Min | Max | Min | Min | Min | Min | Min | Max | Min | Max | Min | %/℃ | %/℃ | (L/D=0.7) |
N54 | 1.50 | 1.45 | 15.0 | 14.5 | 876 | 11 | 836 | 10.5 | 437 | 414 | 55 | 52 | -0.12 | -0.76 | 60 | 140 |
N52 | 1.47 | 1.42 | 14.7 | 14.2 | 876 | 11 | 836 | 10.5 | 422 | 390 | 53 | 49 | -0.12 | -0.76 | 80 | 176 |
N50 | 1.44 | 1.39 | 14.4 | 13.9 | 955 | 12 | 860 | 10.8 | 406 | 374 | 51 | 47 | -0.12 | -0.76 | 80 | 176 |
N48 | 1.42 | 1.37 | 14.2 | 13.7 | 955 | 12 | 860 | 10.8 | 390 | 358 | 49 | 45 | -0.12 | -0.76 | 80 | 176 |
N45 | 1.37 | 1.32 | 13.7 | 13.2 | 955 | 12 | 899 | 11.3 | 366 | 342 | 46 | 43 | -0.12 | -0.76 | 80 | 176 |
N42 | 1.32 | 1.28 | 13.2 | 12.8 | 955 | 12 | 899 | 11.3 | 342 | 318 | 43 | 40 | -0.12 | -0.76 | 80 | 176 |
N40 | 1.28 | 1.25 | 12.8 | 12.5 | 955 | 12 | 899 | 11.3 | 326 | 302 | 41 | 38 | -0.12 | -0.76 | 80 | 176 |
N38 | 1.25 | 1.22 | 12.5 | 12.3 | 955 | 12 | 899 | 11.3 | 310 | 287 | 39 | 36 | -0.12 | -0.76 | 80 | 176 |
N35 | 1.22 | 1.17 | 12.2 | 11.7 | 955 | 12 | 860 | 10.8 | 287 | 263 | 36 | 33 | -0.12 | -0.76 | 80 | 176 |
N33 | 1.17 | 1.13 | 11.7 | 11.3 | 955 | 12 | 836 | 10.5 | 271 | 247 | 34 | 31 | -0.12 | -0.76 | 80 | 176 |
N30 | 1.13 | 1.08 | 11.3 | 10.8 | 955 | 12 | 796 | 10.0 | 247 | 223 | 31 | 28 | -0.12 | -0.76 | 80 | 176 |
N52M | 1.47 | 1.42 | 14.7 | 14.2 | 1114 | 14 | 1035 | 13.0 | 422 | 390 | 53 | 49 | -0.12 | -0.68 | 100 | 212 |
N50M | 1.44 | 1.39 | 14.4 | 13.9 | 1114 | 14 | 1035 | 13.0 | 406 | 374 | 51 | 47 | -0.12 | -0.68 | 100 | 212 |
N48M | 1.42 | 1.36 | 14.2 | 13.6 | 1114 | 14 | 1027 | 12.9 | 390 | 358 | 49 | 45 | -0.12 | -0.68 | 100 | 212 |
N45M | 1.37 | 1.32 | 13.7 | 13.2 | 1114 | 14 | 995 | 12.5 | 366 | 342 | 46 | 43 | -0.12 | -0.68 | 100 | 212 |
N42M | 1.32 | 1.28 | 13.2 | 12.8 | 1114 | 14 | 955 | 12.0 | 342 | 318 | 43 | 40 | -0.12 | -0.68 | 100 | 212 |
N40M | 1.28 | 1.25 | 12.8 | 12.5 | 1114 | 14 | 923 | 11.6 | 326 | 302 | 41 | 38 | -0.12 | -0.68 | 100 | 212 |
N38M | 1.25 | 1.22 | 12.5 | 12.3 | 1114 | 14 | 899 | 11.3 | 310 | 287 | 39 | 36 | -0.12 | -0.68 | 100 | 212 |
N35M | 1.22 | 1.17 | 12.2 | 11.7 | 1114 | 14 | 868 | 10.9 | 287 | 263 | 36 | 33 | -0.12 | -0.68 | 100 | 212 |
N33M | 1.17 | 1.13 | 11.7 | 11.3 | 1114 | 14 | 836 | 10.5 | 271 | 247 | 34 | 31 | -0.12 | -0.68 | 100 | 212 |
N30M | 1.13 | 1.08 | 11.3 | 10.8 | 1114 | 14 | 796 | 10.0 | 247 | 223 | 31 | 28 | -0.12 | -0.68 | 100 | 212 |
N52H | 1.47 | 1.42 | 14.7 | 14.2 | 1274 | 16 | 1043 | 13.1 | 422 | 390 | 53 | 49 | -0.12 | -0.66 | 120 | 248 |
N50H | 1.44 | 1.39 | 14.4 | 13.9 | 1353 | 17 | 1035 | 13.0 | 406 | 374 | 51 | 47 | -0.12 | -0.66 | 120 | 248 |
N48H | 1.42 | 1.36 | 14.2 | 13.6 | 1353 | 17 | 1027 | 12.9 | 390 | 358 | 49 | 45 | -0.12 | -0.66 | 120 | 248 |
N45H | 1.37 | 1.32 | 13.7 | 13.2 | 1353 | 17 | 995 | 12.5 | 366 | 342 | 46 | 43 | -0.12 | -0.66 | 120 | 248 |
N42H | 1.32 | 1.28 | 13.2 | 12.8 | 1353 | 17 | 955 | 12.0 | 342 | 318 | 43 | 40 | -0.12 | -0.66 | 120 | 248 |
N40H | 1.28 | 1.25 | 12.8 | 12.5 | 1353 | 17 | 923 | 11.6 | 326 | 302 | 41 | 38 | -0.12 | -0.66 | 120 | 248 |
N38H | 1.25 | 1.22 | 12.5 | 12.3 | 1353 | 17 | 899 | 11.3 | 310 | 287 | 39 | 36 | -0.12 | -0.66 | 120 | 248 |
N35H | 1.22 | 1.17 | 12.2 | 11.7 | 1353 | 17 | 868 | 10.9 | 287 | 263 | 36 | 33 | -0.12 | -0.66 | 120 | 248 |
N33H | 1.17 | 1.13 | 11.7 | 11.3 | 1353 | 17 | 836 | 10.5 | 271 | 247 | 34 | 31 | -0.12 | -0.66 | 120 | 248 |
N30H | 1.13 | 1.08 | 11.3 | 10.8 | 1353 | 17 | 796 | 10 | 247 | 223 | 31 | 28 | -0.12 | -0.66 | 120 | 248 |
N52SH | 1.44 | 1.42 | 14.4 | 14.2 | 1592 | 20 | 1076 | 13.5 | 422 | 390 | 53 | 49 | -0.12 | -0.66 | 140 | 284 |
N50SH | 1.42 | 1.39 | 14.2 | 13.9 | 1592 | 20 | 1053 | 13.2 | 406 | 374 | 51 | 47 | -0.12 | -0.66 | 140 | 284 |
N48SH | 1.40 | 1.36 | 14.0 | 13.6 | 1592 | 20 | 1035 | 13.0 | 390 | 358 | 49 | 45 | -0.11 | -0.56 | 150 | 302 |
N45SH | 1.37 | 1.32 | 13.7 | 13.2 | 1592 | 20 | 995 | 12.5 | 366 | 342 | 46 | 43 | -0.11 | -0.56 | 150 | 302 |
N42SH | 1.32 | 1.28 | 13.2 | 12.8 | 1592 | 20 | 955 | 12.0 | 342 | 318 | 43 | 40 | -0.11 | -0.56 | 150 | 302 |
N40SH | 1.28 | 1.25 | 12.8 | 12.5 | 1592 | 20 | 939 | 11.8 | 326 | 302 | 41 | 38 | -0.11 | -0.56 | 150 | 302 |
N38SH | 1.25 | 1.22 | 12.5 | 12.2 | 1592 | 20 | 907 | 11.4 | 310 | 287 | 39 | 36 | -0.11 | -0.56 | 150 | 302 |
N35SH | 1.22 | 1.17 | 12.2 | 11.7 | 1592 | 20 | 876 | 11.0 | 287 | 263 | 36 | 33 | -0.11 | -0.56 | 150 | 302 |
N33SH | 1.17 | 1.13 | 11.7 | 11.3 | 1592 | 20 | 844 | 10.6 | 271 | 247 | 34 | 31 | -0.11 | -0.56 | 150 | 302 |
N30SH | 1.13 | 1.08 | 11.3 | 10.8 | 1592 | 20 | 804 | 10.1 | 247 | 223 | 31 | 28 | -0.11 | -0.56 | 150 | 302 |
N28SH | 1.09 | 1.04 | 10.9 | 10.4 | 1592 | 20 | 788 | 9.9 | 223 | 199 | 29 | 25 | -0.11 | -0.56 | 150 | 302 |
N50SHT | 1.42 | 1.39 | 14.2 | 13.9 | 1751 | 22 | 1053 | 13.2 | 406 | 374 | 51 | 47 | -0.11 | -0.56 | 150 | 302 |
N48SHT | 1.40 | 1.36 | 14 | 13.6 | 1751 | 22 | 1031 | 12.9 | 390 | 358 | 49 | 45 | -0.11 | -0.56 | 160 | 320 |
N45SHT | 1.37 | 1.32 | 13.7 | 13.2 | 1751 | 22 | 1003 | 12.6 | 366 | 342 | 46 | 43 | -0.11 | -0.56 | 160 | 320 |
N42SHT | 1.32 | 1.28 | 13.2 | 12.8 | 1751 | 22 | 971 | 12.2 | 342 | 318 | 43 | 40 | -0.11 | -0.53 | 160 | 320 |
N40SHT | 1.28 | 1.25 | 12.8 | 12.5 | 1751 | 22 | 947 | 11.9 | 326 | 302 | 41 | 38 | -0.11 | -0.53 | 160 | 320 |
N38SHT | 1.25 | 1.22 | 12.5 | 12.2 | 1751 | 22 | 923 | 11.6 | 310 | 287 | 39 | 36 | -0.11 | -0.53 | 160 | 320 |
N35SHT | 1.22 | 1.17 | 12.2 | 11.7 | 1751 | 22 | 884 | 11.1 | 287 | 263 | 36 | 33 | -0.11 | -0.53 | 160 | 320 |
N33SHT | 1.17 | 1.13 | 11.7 | 11.3 | 1751 | 22 | 860 | 10.8 | 271 | 247 | 34 | 31 | -0.11 | -0.53 | 160 | 320 |
N30SHT | 1.13 | 1.08 | 11.3 | 10.8 | 1751 | 22 | 812 | 10.2 | 247 | 223 | 31 | 28 | -0.11 | -0.53 | 160 | 320 |
N50UH | 1.42 | 1.39 | 14.2 | 13.9 | 1990 | 25 | 1053 | 13.2 | 406 | 374 | 51 | 47 | -0.11 | -0.53 | 170 | 338 |
N48UH | 1.40 | 1.36 | 14.0 | 13.6 | 1990 | 25 | 1031 | 12.9 | 390 | 358 | 49 | 45 | -0.11 | -0.53 | 180 | 356 |
N45UH | 1.36 | 1.32 | 13.6 | 13.2 | 1990 | 25 | 1003 | 12.6 | 366 | 342 | 46 | 43 | -0.11 | -0.50 | 180 | 356 |
N42UH | 1.32 | 1.28 | 13.2 | 12.8 | 1990 | 25 | 971 | 12.2 | 342 | 318 | 43 | 40 | -0.10 | -0.50 | 180 | 356 |
N40UH | 1.28 | 1.25 | 12.8 | 12.5 | 1990 | 25 | 923 | 11.6 | 326 | 302 | 41 | 38 | -0.10 | -0.50 | 180 | 356 |
N38UH | 1.25 | 1.22 | 12.5 | 12.2 | 1990 | 25 | 907 | 11.4 | 310 | 287 | 39 | 36 | -0.10 | -0.50 | 180 | 356 |
N35UH | 1.22 | 1.17 | 12.2 | 11.7 | 1990 | 25 | 860 | 10.8 | 287 | 263 | 36 | 33 | -0.10 | -0.50 | 180 | 356 |
N33UH | 1.17 | 1.13 | 11.7 | 11.3 | 1990 | 25 | 852 | 10.7 | 271 | 247 | 34 | 31 | -0.10 | -0.50 | 180 | 356 |
N30UH | 1.13 | 1.08 | 11.3 | 10.8 | 1990 | 25 | 812 | 10.2 | 247 | 223 | 31 | 28 | -0.10 | -0.50 | 180 | 356 |
N48VH | 1.40 | 1.36 | 14.0 | 13.6 | 2149 | 27 | 1031 | 12.9 | 390 | 358 | 49 | 45 | -0.10 | -0.50 | 180 | 356 |
N45VH | 1.36 | 1.32 | 13.6 | 13.2 | 2149 | 27 | 1003 | 12.6 | 366 | 342 | 46 | 43 | -0.10 | -0.50 | 190 | 374 |
N42VH | 1.32 | 1.28 | 13.2 | 12.8 | 2149 | 27 | 971 | 12.2 | 342 | 318 | 43 | 40 | -0.10 | -0.50 | 190 | 374 |
N40VH | 1.28 | 1.25 | 12.8 | 12.5 | 2149 | 27 | 947 | 11.9 | 326 | 302 | 41 | 38 | -0.10 | -0.50 | 190 | 374 |
N38VH | 1.25 | 1.22 | 12.5 | 12.2 | 2149 | 27 | 923 | 11.6 | 310 | 287 | 39 | 36 | -0.10 | -0.50 | 190 | 374 |
N35VH | 1.22 | 1.17 | 12.2 | 11.7 | 2149 | 27 | 884 | 11.1 | 287 | 263 | 36 | 33 | -0.10 | -0.50 | 190 | 374 |
N33VH | 1.17 | 1.13 | 11.7 | 11.3 | 2149 | 27 | 860 | 10.8 | 271 | 247 | 34 | 31 | -0.10 | -0.50 | 190 | 374 |
N30VH | 1.13 | 1.08 | 11.3 | 10.8 | 2149 | 27 | 852 | 10.7 | 247 | 223 | 31 | 28 | -0.10 | -0.50 | 190 | 374 |
N48EH | 1.35 | 1.40 | 13.5 | 14 | 2388 | 30 | 1051 | 13.2 | 390 | 358 | 49 | 45 | -0.10 | -0.45 | 200 | 392 |
N45EH | 1.36 | 1.32 | 13.6 | 13.2 | 2388 | 30 | 1031 | 12.9 | 366 | 342 | 46 | 43 | -0.10 | -0.45 | 200 | 392 |
N42EH | 1.32 | 1.28 | 13.2 | 12.8 | 2388 | 30 | 970 | 12.2 | 342 | 318 | 43 | 40 | -0.10 | -0.45 | 200 | 392 |
N40EH | 1.28 | 1.25 | 12.8 | 12.5 | 2388 | 30 | 947 | 11.9 | 326 | 302 | 41 | 38 | -0.10 | -0.45 | 200 | 392 |
N38EH | 1.25 | 1.22 | 12.5 | 12.2 | 2388 | 30 | 915 | 11.5 | 310 | 287 | 39 | 36 | -0.10 | -0.45 | 200 | 392 |
N35EH | 1.22 | 1.17 | 12.2 | 11.7 | 2388 | 30 | 884 | 11.1 | 287 | 263 | 36 | 33 | -0.10 | -0.45 | 200 | 392 |
N33EH | 1.17 | 1.13 | 11.7 | 11.3 | 2388 | 30 | 860 | 10.8 | 271 | 247 | 34 | 31 | -0.10 | -0.45 | 200 | 392 |
N30EH | 1.13 | 1.08 | 11.3 | 10.8 | 2388 | 30 | 820 | 10.3 | 247 | 223 | 31 | 28 | -0.10 | -0.45 | 200 | 392 |
N45FH | 1.36 | 1.32 | 13.6 | 13.2 | 2547 | 32 | 1031 | 12.9 | 366 | 342 | 46 | 43 | -0.10 | -0.45 | 210 | 410 |
N42FH | 1.32 | 1.28 | 13.2 | 12.8 | 2547 | 32 | 970 | 12.2 | 342 | 318 | 43 | 40 | -0.10 | -0.45 | 210 | 410 |
N40FH | 1.28 | 1.25 | 12.8 | 12.5 | 2547 | 32 | 947 | 11.9 | 326 | 302 | 41 | 38 | -0.10 | -0.45 | 210 | 410 |
N38FH | 1.25 | 1.22 | 12.5 | 12.2 | 2547 | 32 | 915 | 11.5 | 310 | 287 | 39 | 36 | -0.10 | -0.45 | 210 | 410 |
N35FH | 1.22 | 1.17 | 12.2 | 11.7 | 2547 | 32 | 884 | 11.1 | 287 | 263 | 36 | 33 | -0.10 | -0.45 | 210 | 410 |
N33FH | 1.17 | 1.13 | 11.7 | 11.3 | 2547 | 32 | 860 | 10.8 | 271 | 247 | 34 | 31 | -0.10 | -0.45 | 210 | 410 |
N30FH | 1.13 | 1.08 | 11.3 | 10.8 | 2547 | 32 | 820 | 10.3 | 247 | 223 | 31 | 28 | -0.10 | -0.45 | 210 | 410 |
N42AH | 1.32 | 1.28 | 13.2 | 12.8 | 2786 | 35 | 970 | 12.2 | 342 | 318 | 43 | 40 | -0.10 | -0.45 | 230 | 446 |
N40AH | 1.28 | 1.25 | 12.8 | 12.5 | 2786 | 35 | 947 | 11.9 | 326 | 302 | 41 | 38 | -0.10 | -0.45 | 230 | 446 |
N38AH | 1.25 | 1.22 | 12.5 | 12.2 | 2786 | 35 | 915 | 11.5 | 310 | 287 | 39 | 36 | -0.10 | -0.45 | 230 | 446 |
N35AH | 1.20 | 1.17 | 12.0 | 11.7 | 2786 | 35 | 883 | 11.1 | 287 | 263 | 36 | 33 | -0.10 | -0.45 | 230 | 446 |
N33AH | 1.17 | 1.11 | 11.7 | 11.1 | 2786 | 35 | 844 | 10.6 | 271 | 239 | 34 | 31 | -0.10 | -0.45 | 230 | 446 |
N30AH | 1.13 | 1.07 | 11.3 | 10.7 | 2786 | 35 | 812 | 10.2 | 247 | 215 | 31 | 27 | -0.10 | -0.45 | 230 | 446 |
N28AH | 1.09 | 1.02 | 10.9 | 10.2 | 2786 | 35 | 772 | 9.7 | 231 | 199 | 29 | 25 | -0.10 | -0.45 | 230 | 446 |
N38TH | 1.25 | 1.22 | 12.5 | 12.2 | 3182 | 40 | 915 | 11.5 | 310 | 287 | 39 | 36 | -0.10 | -0.42 | 260 | 500 |
N35TH | 1.22 | 1.17 | 12.2 | 11.7 | 3182 | 40 | 867 | 10.9 | 287 | 263 | 36 | 33 | -0.10 | -0.42 | 260 | 500 |
N33TH | 1.17 | 1.11 | 11.7 | 11.1 | 3182 | 40 | 851 | 10.7 | 271 | 239 | 34 | 31 | -0.10 | -0.42 | 260 | 500 |
N30TH | 1.13 | 1.08 | 11.3 | 10.8 | 3182 | 40 | 820 | 10.3 | 247 | 223 | 31 | 28 | -0.10 | -0.42 | 260 | 500 |
Coating (surface treatment)
Coating (sintered NdFeB magnets) | Abbreviation | color | thickness (µm) | corrosion resistance (rating 1 to 10) | Recommended working Temp. (℃) | Surface Tension (γ) | ||
SST | HHT | PCT |
Nickel (barrel) | NiCuNi | Bright silver | 10-20 | 5 | 5 | 5 | ≤260 | 36 |
Nickel (rack) | NiCuNi | Bright silver | 10-20 | 4 | 5 | 5 | ≤260 | 36 |
3+Cr Zinc (barrel) | Zn | Blue&white | 5-10 | 4 | 3 | 3 | ≤160 | 38 |
3+Cr Zinc (rack) | Zn | Blue&white | 5-10 | 3 | 3 | 3 | ≤160 | 38 |
3+Cr Color Zinc (barrel) | Colored Zn | Bright color | 5-10 | 3 | 3 | 3 | ≤160 | 38 |
3+Cr Color Zinc (rack) | Colored Zn | Bright color | 5-10 | 3 | 3 | 3 | ≤160 | 38 |
Electroless nickel plating (barrel) | Electroless Ni | Dark silver | 12-20 | 5 | 5 | 4 | ≤260 | 36 |
Electroless nickel plating (rack) | Electroless Ni | Dark silver | 12-20 | 4 | 5 | 4 | ≤260 | 36 |
Nickel+Chromium | Cr | Dark black | 12-20 | 4 | 5 | 5 | ≤260 | 36 |
Teflon | PTFE | Dark grey | 3 | 3 | 3 | ≤260 | 36 | |
Nickel+Black Nickel | Black Ni | Black | 12-20 | 5 | 5 | 5 | ≤260 | 36 |
Nickel+Tin | Sn | Bright silver | 12-20 | 4 | 5 | 5 | – | 36 |
Nickel+Silver | Ag | Silver | 12-20 | 4 | 5 | 5 | – | 36 |
Nickel+Gold | Au | Golden | 10-20 | 4 | 5 | 5 | – | 36 |
Epoxy | Epoxy | Black | 10-20 | 5 | 5 | 4 | ≤160 | 36 |
Nickel+Epoxy | NiCu+Epoxy | Black | 15-25 | 5 | 5 | 3 | ≤160 | 36 |
Passivation/Phosphorization | Phosphate | Dark grey | 1-3 | – | – | – | ≤240 | 37 |
Nano Coating | Nano | Gray/Black | 15-30 | 6 | 6 | 7 | ≤300 | 33 |
Manufacturing Process
Sintered neodymium magnet (Neodymium-Iron-Born or Nd-Fe-B) is an alloy consisting of neodymium, iron, boron, cobalt, varying levels of praseodymium, dysprosium or terbium and other transition metals. The manufacturing process for sintered neodymium magnets are divided into two main stages: powder metallurgy and mechanical processing. There are are six critical manufacturing steps involved in the powder metallurgy stage.
Raw material including PrNd alloy, iron, copper, DyFe, etc. are mixed and melted together according to a certain proportion. These are heated in a vacuum furnace and a stream of molten metal is forced under pressure onto a cooled drum where it is rapidly cooled at approximately 100,000 degrees-per-second. As a result, strip cast NdFeB ingot is produced for further processing
After melting and casting, the NdFeB alloy ingot is subject to hydrogen atmosphere. Hydrogen slowly absorbs into the solid alloy and makes it brittle, which upon milling becomes fine powder. The process is therefore called hydrogen decrepitation.
The NdFeB powder produced from hydrogen decrepitation is protected in an inert gas atmosphere and handled in glove boxes before going to the automated press. The powder are then fed into a grinding chamber, where the high-velocity gas streams are introduced to cause particles clash violently against each other. As a result, extremely fine powder having a size ranging from 3 to 5 μm is produced.
The powder from jet milling is pressed. During the pressing, a strong magnetic field is applied in order to rotate the powder particles so that their main crystal axes are aligned. That’s required to achieve anisotropy, which means that every piece of powder in the finished magnet will contribute to the magnetic field. Without the alignment, the c-axis (crystal axis) would be more or less randomly distributed, and only those particles which are roughly in the direction of the magnetization field would be magnetized, resulting in a significantly weaker magnet.
The pressed NdFeB block is bagged and immersed into a cold isostatic press (CIP) under huge pressure. This process intends to remove the remaining air gaps within the block. NdFeB blocks coming out of CIP become a bit smaller than it was before it goes in.
The pressed blocks are placed in a sintering furnace at an extremely high temperature just below the melting point of the NdFeB alloy. At this temperature of over 1000 degree, the individual atoms have a lot of motion, which enables the NdFeb alloy to develop their full magnetic and mechanical properties. The magnetic domains maintain the same orientation they had before sintering. At this temperature, shrinkage of NdFeB blocks takes place and full density is achieved.
After sintering, there are pent-up stresses in the metal from all the movement during sintering, so the blocks are heat-treated again in a step fashion at lower temperatures to reduce the stresses. The blocks are ramped up to a high holding temperature for a set time and then they are ramped down to a lower holding temperature. Once the holding time is achieved, the now stress-free blocks are slowly cooled to room temperature.
Direction of Magnetization
Sintered neodymium magnets are anisotropic and can only be magnetized in the predetermined direction. Generally, the magnets are axially magnetized (magnet in round shape) or magnetized through thickness (magnet in square or rectangular shape).
However, it’s not uncommon to find a neodymium disc magnet diametrically magnetized because it’s used as rotary position sensor. Besides simple two-pole magnetization, sintered neodymium magnets can also be magnetized in sectors. Examples of different magnetization patterns are given below. (Sinter neodymium magnets in ring shape can have axial, diametrical, or radial magnetization. Arc magnets are usually diametrically magnetized in pair since they are used in electric motors. Thus the name, arc motor magnets.

Maximum Working Temperature of Neodymium Magnets
Sintered neodymium magnets are characterized by their excellent magnetic performance at room temperature. However, they have the least temperature resistance compared to other permanent magnets. N grade magnet only has a theoretical temperature limit of 80°C. (The practical maximum operating temperature is related to the L/D ratio of the magnet.)
For higher temperature resistance, high-cost heavy rare earth elements (HREEs) are needed to increase the magnet coercivity. Even with the help of grain boundary diffusion (GBD) technology, less heavy rare earth is needed to increase the coercivity, the cost to produce sintered neodymium magnets that can withstand temperature over 200°C is still very high. That’s why the market for Samarium-Cobalt magnets still widely exists in e.g. aerospace, military industry, etc.
Hitachi Licensed Neodymium Magnets
Raw Material "NdPr Price" | Neodymium Magnet Price
Neodymium magnets are known for its high price, but more importantly for its price volatility. Rare earth alloy – NdPr alloy is the determinant of the magnet price change. PrNd alloy is of vital importance to the production and cost of all types of neodymium magnets. It’s also an indictor of price trend of neodymium magnets.
