Magnets
From Pickupedia
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MAGNETIC MATERIALS
Guitar pickups require a magnet of some kind, most often Alnico alloy,
although annealed steel and CuNiFe were used in early pickups, samarium
cobalt has appeared in some Fender Noiseless, and a few neodymium alloy
pickups have come into production in the last decade.
ALNICO MAGNETS
Alnico alloys are so called because, while roughly 50% iron (Fe),
they significantly contain Aluminum, Nickel, and Cobalt.
Most Alnico alloys also contain copper (Cu)
and the later ones also contain Titanium.
Although Alnico 3 uniquely contains Copper (Cu)
but no Cobalt, good sense prevailed over syntactic
nitpicking and the name AlNiCu never made it into history.
| Alloy | Al% | Ni% | Co% | Cu% | Ti% | Fe% | BHmax
(MGOe) | Br
(gauss) | Hc
(oersteds) | Hci
(oersteds) |
| Alnico 1 | 12 | 21 | 5 | 3 | - | 59 | 1.4 | 7200 | 470 | 480 |
| Alnico 2 | 10 | 19 | 13 | 3 | - | 55 | 1.7 | 7500 | 560 | 580 |
| Alnico 3 | 12 | 25 | - | 3 | - | 60 | 1.35 | 7000 | 480 | 500 |
| Alnico 4 | 12 | 28 | 5 | - | - | 65 | 1.35 | 5600 | 720 | 720 |
| Alnico 5 | 8 | 14 | 24 | 3 | - | 51 | 5.5 | 12800 | 640 | 640 |
| Alnico 5DG | 8 | 14 | 24 | 3 | - | 51 | 6.5 | 13300 | 670 | 670 |
| Alnico 5-7 | 8 | 14 | 24 | 3 | - | 51 | 7.5 | 13500 | 740 | 740 |
| Alnico 6 | 8 | 16 | 24 | 3 | 1 | 58 | 3.9 | 10500 | 780 | 800 |
| Alnico 8 | 7 | 15 | 35 | 4 | 5 | 34 | 5.3 | 8200 | 1650 | 1860 |
| Alnico 8HC | 8 | 14 | 38 | 3 | 8 | 29 | 5.0 | 7200 | 1900 | 2170 |
| Alnico 9 | 7 | 15 | 35 | 4 | 5 | 34 | 9.0 | 10600 | 1500 | 1500 |
Notes: The three most significant permanent magnet characteristics are
- Remanence (Br), a measure of magnetic attraction
- Coercivity (Hc), resistance to an opposing magnetic field,
- maximum energy product (BHmax)
BHmax is the product of remanence and coercivity and indicates
the maximum work you can get out of a magnetic material.
This chart is an amended form of the page 7 table in the
permanent magnet standards document MMPA 0100-00.
Alnico 4 properties were added after the fact.
CERAMIC MAGNETS
Ceramic magnets are a mixture of barium and strontium with ferric oxide.
While their limiting remanence (magnetic pull) is lower than that of Alnico alloys,
its coercivity (resistance to demagnetization) is much higher and allows the production
of smaller, more square rectilinear shaped magnets than are practical with Alnico.
In practical terms, up to a point, small ceramic magnets
are often stronger than same size Alnico magnets.
| MMPA Designation | MMPA Class | BHmax (MGOe) | Remanence (Br) | Coercivity (Hc) |
| 1.0/3.3 | Ceramic 1 | 1.05 | 2300 | 1860 |
| 3.4/2.5 | Ceramic 5 | 3.40 | 3800 | 2400 |
| 2.7/4.0 | Ceramic 7 | 2.75 | 3400 | 3250 |
| 3.5/3.1 | Ceramic 8 | 3.50 | 3850 | 2950 |
| 3.4/3.9 | - | 3.40 | 3800 | 3400 |
| 4.0/2.9 | - | 4.00 | 4100 | 2800 |
| 3.2/4.8 | - | 3.20 | 3700 | 3500 |
| 3.8/4.0 | - | 3.80 | 4000 | 3650 |
This chart is a condensed form of the page 12 table in the
permanent magnet standards document MMPA 0100-00.
OTHER MAGNETICS MATERIALS
...but Wait! There are other unusual magnetic materials,
some not so permanent, as their Hci number below 500 suggest.
This is important because the Charlie Christian pickup used
an undisclosed steel alloy, and later CuNiFe while the
Telecaster Wide Range of the 1970's used CuNiFe pole pieces.
In short, it is completely reasonable to make pickups having magnets other than Alnico or Ceramic 5.
| Magnetic Materials | BHmax
(MGOe) | Br
gauss | Hc/Hci
Oersteds |
|---|---|---|---|
| 31/2% Cr Steel | 0.13 | 10300 | 60 |
| 3% Co Steel | 0.38 | 9700 | 80 |
| 17% Co Steel | 0.69 | 10700 | 160 |
| 38% Co Steel | 0.98 | 10400 | 230 |
| Ceramic 2 | 1.80 | 2900 | 2400/3000 |
| Ceramic 6 | 2.45 | 3200 | 2820/3300 |
| Alnico 4 | 1.35 | 5600 | 720 |
| PtCo | 9.00 | 6450 | 4000 |
| Vicalloy 1 | 0.80 | 7500 | 250 |
| Remalloy | 1.00 | 9700 | 250 |
| Cunife 1 | 1.40 | 5500 | 530 |
| MnAlC | 5.00 | 5450 | 2550/3150 |
| RE Cobalt 5/16 | 5.00 | 4700 | 4500/16000 |
| RE Cobalt 14/14 | 14.00 | 7500 | 700/14000 |
This chart is a condensed form of the appendix A page 25 table in the
permanent magnet standards document MMPA 0100-00.
