Choosing a magnet usually starts with one question: which material family? The four main ones — NdFeB, SmCo, ferrite and AlNiCo — differ in strength, heat tolerance, corrosion and cost. Here they are side by side.
The comparison table
| Property | NdFeB | SmCo | Ferrite | AlNiCo |
|---|---|---|---|---|
| Strength (BH)max | 25–55 MGOe | 16–35 MGOe | 1–4 MGOe | ~10 MGOe |
| Max temp. | 80–230 °C by grade | 250–350 °C | ~250 °C | 450–550 °C |
| Corrosion | Poor — needs coating | Excellent | Excellent | Good |
| Relative cost | Moderate | High | Lowest | High |
| Typical uses | Motors, speakers, sensors | Aerospace, high-temp | Fridge magnets, toys | Instruments, audio |
Typical commercial ranges — confirm with the supplier's data sheet.
NdFeB — the strong one
The strongest family, up to 55 MGOe, and by far the most common: motors, headphones, wind turbines, sensors. It is brittle, dislikes heat above ~200 °C, and corrodes easily — so it is always coated. See what is NdFeB.
SmCo — the heat-resistant one
Almost as strong as NdFeB and far more heat-tolerant (250–350 °C), with excellent corrosion resistance. The catch is price: samarium and cobalt are expensive. Aerospace and defense use it where heat matters more than budget.
Ferrite — the cheap workhorse
Weak — roughly a tenth of NdFeB's energy — but extremely cheap, corrosion-proof and easy to magnetize. You pay in size: a ferrite part matching an N42 block can be many times bigger. Fridge magnets are ferrite.
AlNiCo — the old specialist
Moderate strength, superb heat tolerance (up to 550 °C) and excellent long-term stability. Its coercivity is low, so it demagnetizes easily and needs careful design. Classic in instruments and high-end audio.
How to choose
Maximum strength in a small size? NdFeB. Sustained heat above ~200 °C? SmCo or AlNiCo. Outdoor, humid, tight budget? Ferrite. Define the environment first, and the material chooses itself.
Read on: four key parameters → · grades explained →