The Alnico (Aluminum, Nickel, Cobalt) family was introduced in the 1930's. AlNICo magnets derive their magnetic properties and their name from their main constituents - aluminum, nickel, and cobalt. They have the widest range of temperature stability of any standard magnetic material, It's characterized by excellent temperature stability, high residual induction, and relatively high energies. These were the first materials specifically designed for permanent magnets to be used in meters and instruments commercially. As one of the oldest members of our magnet family, Alnico remains the workhorse of the permanent magnet industry and can be relied upon to deliver impressive flux density at an economical price. Alnico also boasts the lowest temperature coefficient of any commercial magnet material (0.02% per degree centigrade) allowing for excellent stability over a wide temperature range.

Alnico is available in both cast,sintered and bonded forms. Sintered Alnico offer slightly lower magnetic properties but better mechanical characteristics than cast Alnico. These materials are brittle, hard and cannot effectively be machined by conventional techniques other than by grinding.

Advantages for using Alnico:

Excellent temperature characteristics
Capable of working at a wide range of temperature up to 550 degrees centigrade.
High field strengths at medium prices
Easy of magnetizing,The lower coercive force of Alnico makes magnetizing a simple matter in most cases
Compatible with most painting or plating systems (including nickel and copper)

Charasteristics:

Suitable for small volume magnet with complex shape;
Compact crystal, high intensity;
Regular shape, precision size;
Even elements, stable performance;
Suitable for compound magnet;
Excellent temperature stability (temp. coefficient of Br is the smallest among all of the other permanent magnets.)

DESIGN CONSIDERATIONS
Because Alnico magnets are coarse-grained, hard and brittle, they cannot be drilled or conventionally machined. Given these mechanical properties, Alnico parts are not normally used as structural members. Where a choice exists, select simple shapes. Slots are preferred over holes. Cross sections of less than 0.125" (3.18 mm) should be avoided. Finished surfaces, when required, may be produced by grinding; however, for many applications, the "as cast" or "as sintered" surface yields a satisfactory result at a significantly lower cost. To facilitate mounting and give adequate protection to the magnet, special assemblies such as rotors and magnetron magnets may be supplied with an aluminum jacket. Additionally, low carbon steel pole pieces may be attached to magnet pole faces by adhesive bonding or with studs or bolts. Plastisol or paint can be applied for improved appearance.

Application:

Commercially viable Alnico magnets have been in production since the mid 1940s. Many applications that originally utilized Alnico have switched to Ceramic or Rare Earth magnets. Most new applications do not employ alnico alloy unless the magnets are exposed to high heat or corrosive environments. Alnico magnets are used extensively in aerospace applications, automotive, consumer goods, and medical devices.

Main applications are:

Inner magnetic voltmeter/ammeter, electronic type power energy measuring instrument,avometer,flowmeter;
A wide range of magnetic sensor, polarized relay ,temperature and pressure controller;
Buzzer of Mobile phone, hearing aids, mini speaker;
lighter of automobile, odometer of automobile and motorcycle, permanent motor, adsorptive appliance;
Alnico has experienced renewed interest in recent years in such temperature-sensitive applications as hall-effect and MR-based automotive and electronic sensors, in addition to the traditional magnetron, TWT amplifiers, actuators, motors and instruments applications that have long relied upon Alnico.