Alnico loudspeakers were used in some of the earlier permanent magnet drivers. They tended to be longer in axial length to allow for higher performance and reducing demagnetizing effects (as they have lower coercivity, Hc, than other magnet materials). But with good design, alnico magnets can provide magnetic fields in the air gap which perform as well as those of NdFeB (albeit with greater axial length). However, the alnico material is easy to magnetize and deliberately weaken which can allow for precision tuning of the magnetic field in the air gap to a specific field strength value for optimum acoustic performance (the magnetization is performed on a complete sub-assembly magnet already assembled within steelwork).
Cast and sintered alnico magnets also provide extremely good temperature coefficients resulting in the smallest variation in magnetic output with temperature variation which may be advantageous to acoustic purists. So although NdFeB magnets have tended to replace alnico magnets, the alnico magnet is still used in precision drivers and alnico, by having better corrosion resistance than neodymium, is used in more external applications such as horns. Sometimes the alnico is tapered to derive more performance out of the alnico while reducing leakage and minimizing demagnetization risk.
1. Good chemistry stability and strong anti-corrosion
2. Excellent stability and magnetic performance
3. Various shapes and size
4. High working temperatureÂ
5. Strong magnetic force
6. High intrinsic coercive force
The Alnico magnet is the magnetic element with the highest stability at extreme temperatures, that is, it maintains all its magnetic properties between -250ºC and 425ºC, ensuring a high thermal resistance. (In the case of neodymium magnets, the maximum working temperature is 200°C)
This alloy composed of aluminum, nickel and cobalt, has a high level of magnetic induction but a lower coercivity.
Although new stronger materials and cheaper solutions have emerged, alnico magnets continue to incorporate a special property, have a lower coercive field that enables magnetization and demagnetization, with low power.
The magnetic orientation of these products must be carried out during their heat treatment, ensuring a magnetic field with the direction of magnetization defined. The force that alnico magnets can provide is the most similar and comparable to neodymium magnets.
Another great advantage is its resistance to chemical products, such as acids or solvents, and its good oxidation behavior.
The high temperatures with which alnico magnets can work, together with the thermal resistance and its great strength opens a wide range of possibilities in different industrial sectors. Being a perfect alternative to materials such as neodymium or ferrite.