Magnetic Performance Parameters

Neodymium Magnet Grades:

Many grades of Neodymium magnets exist to support a variety of industrial applications. The range of Neo grades typically extends from 33 MGOe to 52 MGOe. This range allows for optimizing cost, performance, and operational temperature resistance.

The typical convention for “Grade” is to use the value of the particular magnet alloy’s Energy Density or Maximum Energy Product. Oftentimes there are letters or a two digit number suffix attached to the Grade which indicates the Intrinsic Coercive Force (Hci) level of the magnet alloy. This Hci is a good indicator of the maximum allowable temperature a particular Neo alloy can tolerate before irreversible demagnetizing occurs.

The higher the “Grade number” then the higher the Energy Density. Usually the higher the Energy Density the stronger the magnet, but this is very much dependent upon the magnet’s operational environment.

1.Magnetic Property Distribution Chart:

Magnetic Property Distribution

Magnetic Property Distribution

 

2.Magnetic Properties of Sintered NdFeB Magnets:

3. Typical Physical Properties:

Samarium Cobalt Magnet Grades:

Samarium Cobalt magnets (SmCo) is the sister Rare Earth Magnet to NdFeB. SmCo is sometimes called a Rare Earth Cobalt magnet. SmCo magnets exist in two alloy varieties.

Sm1Co5 (SmCo1:5) is the original SmCo alloy.
Sm2Co17 (SmCo2:17) is the more common used and stronger SmCo alloy with SmCo26 being the most popular variety.
Sm1Co5 contains mainly Sm and Co and contains no iron (Fe) so it has excellent corrosion resistance -it should never corrode with water.

Sm2Co17 is mainly Sm and Co but also contains Cu, Hf &/or Zr, sometimes Pr, and Fe. The low free iron content in Sm2Co17 means it is technically prone to a little surface corrosion when in water.

Sm2Co17 is regarded as having good to very good corrosion resistance (far superior to NdFeB) in most applications. A simple coating of NiCuNi will very likely solve any risk of corrosion.

1, Magnetic Property

Sm1Co5 grade

Sm1Co5 grade

Sm2Co17 grade

Sm2Co17 grade

2, Corrosion Resistance

Corrosion resistance:- SmCo(1:5) Exellent (has no iron); SmCo(2:17) Good to Very Good (has some free iron). SmCo magnets can usually be used in humid applications without any need for a protective coating. In wet envrironments, coating of SmCo(2:17) in NiCuNi is recommended to avoid surface corrosion issues. NiCuNi plated SmCo is claimed by some to limit chipping and allows for soldering as well but is rarely done.

Physical Characteristics (excluding bonded variants)

Physical Characteristics of SmCo

Physical Characteristics of SmCo

Alnico Magnet Grades:

The range of Alnico magnet alloy grades available from MPCO Magnetics typically extends from 1.5 – 5.25 MGOe for sintered Alnico and 5.0 – 9.0 for cast Alnico. This range allows for optimizing the cost, performance, and operational temperature resistance for a wide range of applications.

Sintered Alncio magnets are made with a powdered metal process. Lower grades are Isotropic, which can be magnetized in any direction, but at a loss of magnetic strength. The powder metal version of Alnico allows for easier integration of features since a tool is used and the magnet is finished to near net shape. (Sometimes the tooling cost can be a project inhibitor for small production quantities.) Cast Alnico magnets are cast in sand molds and usually require finish grinding. Casting Alnico is the most typical manufacturing method and most cast Alncio is “orientated” and anisotropic. This means that the magnet can only be magnetized in one direction, but this improves the magnetic strength.

Sintered Alnico – Available Grades
Grade Residual
Induction
Br
Coercive
Force
Hc
Intrinsic
Coercive
Force
Hci
Maximum
Energy
Product
(BH)max
Max.
Operating
Temp.*
Nominal Nominal Minimum Nominal Nominal
k-Gauss Tesla Oersted kA/m Oersted kA/m MGOe kJ/m3 °C °F
Alnico 2 7.0 0.7 500 40 540 43 1.5 12 450°C 840°F
Alnico 5 11.0 1.1 600 48 600 48 4.25 34 450°C 840°F
Alnico 8 8.8 0.88 1,530 121 1.600 127 5.25 42 450°C 840°F
* The listed maximum operating temperatures are based on an adequate Length to Diameter ratio or a properly designed magnetic circuit. The listed values are for reference and validation must occur before one chooses a design path.

 

Cast Alnico – Available Grades
Grade Residual
Induction
Br
Coercive
Force
Hc
Intrinsic
Coercive
Force
Hci
Maximum
Energy
Product
(BH)max
Max.
Operating
Temp.*
Nominal Nominal Minimum Nominal Nominal
k-Gauss Tesla k-Oersted kA/m k-Oersted kA/m MGOe kJ/m3 °C °F
Alnico 5 12.2 1.22 600 48 630 50 5.0 40 500°C 930°F
Alnico 5B 12.2 1.22 650 52 660 53 5.5 44 500°C 930°F
Alnico 5 DG 12.5 1.25 690 55 700 56 6.5 52 500°C 930°F
Alnico 5-7 13.0 1.3 700 56 740 59 7.5 60 525°C 980°F
Alnico 8-HC 7.0 0.7 1,750 139 1,750 139 4.5 36 525°C 980°F
Alnico 8 8.2 0.82 1,500 119 1,600 127 5.0 40 525°C 980°F
Alnico 8B 8.8 0.88 1,500 119 1,650 131 5.5 44 525°C 980°F
Alnico 8C 9.0 0.9 1,380 110 1,440 115 7.5 60 525°C 980°F
Alnico 9 10.5 1.05 1,410 112 1,440 139 9.0 72 525°C 980°F
* The listed maximum operating temperatures are based on an adequate Length to Diameter ratio or a properly designed magnetic circuit. The listed values are for reference and validation must occur before one chooses a design path.

 

Reversible Temperature Coefficient for Cast and Sintered Alnico
Temperature Range
(°C)
Induction Br (α)
(%)/°C
Intrinsic Coercivity Hci (β)
(%)/°C
20°C to 150°C -0.02 to -0.03 -0.02 to -0.03
α = Δ Br / Δ T * 100 (Br @ 20°C) [ΔT = 20°C – 150°C]
β = Δ Hci / Δ T * 100 (Hci @ 20°C) [ΔT = 20°C – 150°C]

 

Alnico Magnets – Physical Properties
Property Units Value Sintered Alnico Value Cast Alnico
Vickers Hardness Hv 440 440-620
Density g/cm3 6.8 – 7.0 6.9 – 7.3
Curie Temp TC °C 810 – 860 740 – 860
Curie Temp TF °F 1,400 – 1,580 1,460 – 1,580
Specific Resistance μΩ⋅Cm 50- 70 45 – 75
Bending Strength kN/mm2 0.35 – 0.76 0.05 – 0.31
Tensile Strength kN/mm2 0.35- 0.45 0.02 – 0.15
Thermal Expansion °C-1 +11.0 to +12.4 x10-6 +11.0 to +13.0 x10-6
The listed values are approximate and should be used as a reference. Any magnetic or physical characteristics should be substantiated before selecting a magnet material.

Ferrite & Ceramic Magnet Grades:

The range of Ceramic magnet alloy grades available from MPCO Magnetic Products typically extends from 1.05 – 3.8 MGOe. This range allows for optimizing the cost, performance, and operational temperature resistance for a wide range of applications.

Ceramic magnets have the lowest Energy Density of the commercially viable alloys, but are by far the most cost effective. Oftentimes sacrificing “space” and using more Ceramic / ferrite magnet alloy is a very good-trade-off for the low cost. As with all magnet alloys, Ceramic magnets should not be used as structural elements. They are very inherently brittle and will fracture or chip easily when mechanically stressed.

Ceramic / Strontium Ferrite Magnets – Available Grades
Grade Residual
Induction
Br
Coercive
Force
Hc
Intrinsic
Coercive
Force
Hci
Maximum
Energy
Product
(BH)max
Max.
Operating
Temp.*
Nominal Nominal Minimum Nominal Nominal
k-Gauss Tesla k-Oersted kA/m k-Oersted kA/m MGOe kJ/m3 °C °F
Ceramic 1 2.3 230 1.860 148 3.500 278 1.05 8.4 250° 482°
Ceramic 5 3.9 390 2.400 200 2.500 198 3.4 27.6 250° 482°
Ceramic 8 3.9 390 3.000 240 3.200 256 3.4 27.6 250° 482°
Ceramic 8B 4.0 400 3.000 240 3.050 244 3.8 30.4 250° 482°
* The listed maximum operating temperatures are based on an adequate Length to Diameter ratio or a properly designed magnetic circuit. The listed values are for reference and validation must occur before one chooses a design path.

 

Reversible Temperature Coefficient – Ceramic (Strontium Ferrite) Magnets
Temperature Range
(°C)
Induction Br (α)
(%)/°C
Intrinsic Coercivity Hci (β)
(%)/°C
20°C to 150°C -0.2 to -0.3 0.2 to 0.5
α = Δ Br / Δ T * 100 (Br @ 20°C) [ΔT = 20°C – 150°C]
β = Δ Hci / Δ T * 100 (Hci @ 20°C) [ΔT = 20°C – 150°C]

 

Ceramic Magnets – Physical Properties
Property Units Value Ceramic (Strontium Ferrite)
Vickers Hardness Hv ~ 1160 (7 Mohs)
Density g/cm3 4.5 to 5.1
Curie Temp TC °C 450 to 460
Curie Temp TF °F 840 to 860
*Specific Resistance μΩ⋅Cm > 106
Bending Strength kN/mm2 0.05 – 0.09
Tensile Strength kN/mm2 .02 to .05
Thermal Expansion (∥) °C-1 +11.0 to +16.0 x10-6
Thermal Expansion (⊥) °C-1 ‘+7.0 to +15.0 x 10-6
* The effective resistance may change based on the powder blend. Barium Ferrite has higher resistivity than Strontium Ferrite. Some Ceramic magnets are a blend. To ensure the correct design path is chosen execute due diligence by evaluating the magnet alloy on a case by case basis.