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Neodymium Iron Boron vs. Samarium Cobalt


Often times, questions arise whether it is better to use Neodymium Iron Boron or Samarium Cobalt in an application.

Here are some comparisons; they are limited to the sintered series, no consideration is given to the bonded series. The boxes with the light blue background indicate application/requirement. The boxes with the light yellow background indicate excellence in this application/requirement area.

Neodymium Iron Boron (NdFeB)

Samarium Cobalt (SmCo)

High Temperature Applications

Higher Hci materials can be used as high as 200°C, moderate Hci materials should be used around 150°C. Low Hci materials should be used under 100°C

SmCo can be used at substantially higher temperatures than NdFeB. The material can take continuous temperatures above 250°C

Loss of flux density at elevated temperatures (see temperature effects on magnets for more information)

Loses 0.11% of Br/°C. See Temperature effects on Br and Hci of NdFeB

Loses about 0.03% of Br/°C

Humid environments

Surface treatment should be used. Options are nickel or polymer coatings such as PR1010, or PM1000. Oxidation can be a problem

Surface treatment is not required. Does not oxidize

Cost of part

Lower cost generally

Typically higher cost than NdFeB

Mechanical Strength

Mechanically very strong, not as brittle as SmCo

Brittle

Clean Room environments

Surface treatment is recommended

Surface treatment is not required

Vacuum Applications

Does not need to be coated, however, if desired, Nickel or IVD is recommended. Polymer coatings such as PR1010 can be used, but not recommended in ultra high vacuum or high temperature applications in vacuum due to outgassing. Nickel and IVD are metallic and therefore do not outgas

Surface treatment is not required. However, the material is fairly porous; parts may outgas for a limited duration before high vacuums can be achieved

Aerospace applications

Gaining popularity in aerospace applications. Being used with and without surface treatments. Used on aircrafts, missiles, and satellite programs very successfully. Also qualified and used on the Space Station

Very popular in aerospace and defense applications. Has substantial history in military, aerospace and defense applications

Salt Environments, open seas, and salt spray environments

Care should be taken, surface treatment MUST be used, limited life should be expected

Stable in this environment

Acid environments

Surface treatment is necessary, limited life can be expected

Stable in this environment, however, qualification tests recommended

Alkaline environments

Surface treatment is necessary, limited life can be expected

Stable in this environment, however, qualification tests recommended

Thin walled, thin cross-section applications (a dimension below 0.040")

Mechanically stable, parts have been made as thin as 0.008” thick

Not very good in very thin cross-sections. Under 0.020” is not recommended

Single piece large parts

Better than SmCo, larger blocks can be sintered

Larger blocks (over 3” in any dimension) are challenging

Nickel Plating

Available

Available

PR1010 coating

Available

Available

Radial ring configuration (so as to obtain a true radially oriented field)

Available for custom parts.

Not available

Sensitivity of Flux Density, Br, and Coercivity, Hc, to temperature changes

The Temperature Coefficient of Br (%/°C) ranges from NEGATIVE (0.11 to 0.13). Higher coercivity materials (>20 kOe) are closer to negative (0.11)

The Temperature Coefficient of Hc (%/°C) ranges from NEGATIVE (0.51 to 0.77). The higher the intrinsic coercivity, the lower the Temperature Coefficient of Hc

The Temperature Coefficient of Br (%/°C) ranges from NEGATIVE (0.03 to 0.04). Series Sm2Co17 are less sensitive to temperature changes (around negative 0.03) than SmCo5 (around negative 0.04)

The Temperature Coefficient of Hc (%/°C) ranges from NEGATIVE (0.15 to 0.24). Series Sm2Co17 are less sensitive to temperature changes (around negative 0.15) than SmCo5 (around negative 0.24)