Before rare-earth magnets existed, one alloy ruled the world: AlNiCo. Made from aluminum, nickel, cobalt and iron, it was the strongest permanent magnet you could buy anywhere until the 1970s. Rare earths and cheap ferrite pushed it out of most products — but in two areas AlNiCo is still untouchable.
AlNiCo's superpower: temperature stability
Most magnets lose a noticeable slice of strength as they heat up. AlNiCo barely notices. Its temperature coefficient is the lowest of any magnet family, so its magnetic field stays almost constant from cold to hot — and drifts very little over time, which is why instruments built decades ago still read accurately. It also keeps working at 450-550 °C — temperatures that permanently destroy NdFeB and outlast even SmCo.
The weakness
AlNiCo holds a strong field, but it does not hold it stubbornly. Its resistance to demagnetization (coercivity) is low, so a hard knock, a strong opposing magnet or a careless drop can weaken it. Engineers work around this with long, thin pole shapes and careful circuit design.
Where AlNiCo still shines
- Precision instruments and meters — where a reading must stay stable for years.
- Automotive and industrial sensors — exposed to engine heat.
- High-end loudspeakers — audiophiles still prize its steady field.
- Military and aerospace equipment — where extreme heat is routine.
AlNiCo is the veteran of the magnet family: old, expensive and far from the strongest — but nobody else matches its combination of heat tolerance and rock-steady performance.
Read on: SmCo magnets — built for high temperatures → · why heat hurts magnets →