Magnet

Magnet Information

In general, there are four families of magnets available commercially. Factors such as operating temperature, demagnetizing effects, field strength, environmental characteristics, and available space for movement etc. need to be considered before selecting a magnet for a reed switch or reed sensor application. An overview of each of the families of magnets is given below. A list of our standard magnets is available here.

NdFeB

• Red color bulletHighest energy product
• Red color bulletVery high remanance and coercivity
• Red color bulletRelatively low priced
• Red color bulletMechanically stronger than SmCo
• Red color bulletSome grades can be used up to 200°C
• Red color bulletNot recommended in Hydrogen atmosphere
• Red color bulletBonded types can be machined but not tapped

SmCo

• High energy product
• Suitable for high performance applications
• High resistance to demagnetization
• Excellent thermal stability
• High corrosion resistance
• Most expensive magnet
• Can be used up to 300°C
• Prone to chipping - should not be used as a structure

AlNiCo

• Cheaper than rare earth magnets
• Highest working temperature of 550°C
• Lowest temperature coefficient
• Low coercivity when compared to other types
• High induction levels

Ferrites

• Ferrites
• Poor thermal stability
• Cheapest of all types
• Can be used up to 300°C
• Needs grinding to meet tight tolerances
• High corrosion resistance

Magnet Selection Guide

Cost	Ferrite	AlNiCo	NdFeB	SmCo
Energy	Ferrite	AlNiCo	SmCo	NdFeB
Operating Temperature	NdFeB	Ferrite	SmCo	AlNiCo
Corrosion Resistance	NdFeB	SmCo	SmCo	Ferrite
Resistance to Demagnetization	AlNiCo	Ferrite	NdFeB	NdFeB
Mechanical Strength	Ferrite	SmCo	NdFeB	AlNiCo
Temperature Coefficient	AlNiCo	SmCo	NdFeB	SmCo

Units Conversion Table

Property	CGS Unit	SI Unit	Conversion Factor
Magnetic Flux	Maxwell	Weber	1 Weber = 106 Lines
Flux Density (B)	Gauss	Tesla	1 Tesla = 104 Gauss
Magnetomotive force	Gilbert	Ampere-turn (AT)	1 Gilbert = 0.796 AT
Magnetizing force field (H)	Oersted	Ampere-turn / metre	1 Oersted = 79.577 AT / m