Radial and diametric magnetization describe two very different magnetic-field orientations. In a diametrically magnetized round magnet, the north and south poles are on opposite sides of the curved surface and the magnetization runs across one diameter. In a true radially magnetized ring, the local magnetization direction points inward or outward around the circumference; in a simple two-pole design, the inner and outer circumferences have opposite polarity.
The magnet’s shape does not define its magnetization direction. A ring can be axial, diametric, true radial or multipole. That distinction is critical in rotary sensors, encoders, motors, couplings and other OEM assemblies.
| Magnetization | Where the poles are | Common geometry | Typical use |
|---|---|---|---|
| Axial | Opposite flat faces | Discs, rings, blocks | Holding, general assemblies, many stock magnets |
| Diametric | Opposite sides of the curved surface | Discs, cylinders, rings | Rotary sensors, encoders, shaft-angle sensing |
| True radial | Typically inner vs. outer circumference in a simple two-pole ring | Ring / annular | Motors, generators, couplings, specialized rotary magnetic circuits |
| Multipole ring | Multiple alternating poles around a circumference or face | Ring | Encoders, motors, commutation and specialized sensing |
For a broader overview of all orientations, see Magnetization Directions Explained. To compare stocked annular parts, browse Ring Magnets.
What Is Diametric Magnetization?
A diametrically magnetized magnet is magnetized across one diameter of a round part rather than along its central axis. The north and south poles are therefore located on opposite sides of the curved surface.
Diametric magnetization is especially useful in rotary position sensing. When a diametrically magnetized disc, cylinder or ring rotates with a shaft, its field direction rotates with it. A Hall-effect, AMR, GMR or TMR sensor can use that changing field direction to determine angular position.
- Magnetization direction: one straight axis across the diameter.
- Pole locations: opposite sides of the curved surface.
- Common shapes: discs, cylinders and rings.
- Common applications: rotary encoders, shaft-angle sensors, knobs, valve-position sensing and compact rotary assemblies.
For sensor-specific design guidance, see How Sensor Magnets Work, Magnet Field Distance Calculator, or browse Sensor Magnets.
What Is Radial Magnetization?
Radial magnetization is most commonly associated with ring magnets. In a true radial ring, the local magnetization vector changes continuously as you move around the circumference because it follows the radius of the ring rather than one fixed global axis.
In the simplest two-pole true-radial ring, magnetic flux is directed between the inner diameter and outer diameter. More complex radial multipole patterns can also be engineered when an application needs several alternating poles around the ring.
- Magnetization direction: locally inward or outward along radial directions.
- Typical geometry: one-piece ring or annular magnet.
- Common applications: permanent-magnet motors, generators, magnetic couplings, bearings and custom rotary assemblies.
- Manufacturing: usually more specialized than standard axial magnetization.
For the detailed distinction between a standard ring and a true radial ring, read What Is a True Radial Magnet?.
Radial vs. Diametric Magnetization
| Feature | Diametric | True radial |
|---|---|---|
| Magnetization path | One straight direction across the diameter | Direction changes continuously around the ring |
| Typical pole arrangement | Opposite sides of curved surface | Inner vs. outer circumference for a simple two-pole ring |
| Common shapes | Disc, cylinder, ring | Primarily ring / annular |
| Best-known use | Rotary position sensing | Rotary magnetic circuits, motors and couplings |
| Typical sourcing | Often custom, but relatively conventional | Usually engineered/custom |
How Is Axial Magnetization Different?
An axially magnetized disc or ring is magnetized along its centerline, so the poles are on the two flat faces. This is the most common orientation for many stocked disc and ring magnets.
A useful way to remember the three orientations is:
- Axial: through the thickness.
- Diametric: across one diameter.
- Radial: inward/outward along local radii around a ring.
Can a Ring Magnet Be Diametrically Magnetized?
Yes. A ring describes the geometry, not the pole orientation. A ring can be axially magnetized, diametrically magnetized, radially magnetized or magnetized with multiple poles. That is why an OEM drawing should always call out both the physical dimensions and the magnetization pattern.
If you only specify “ring magnet,” a supplier cannot infer whether the poles should be on the flat faces, opposite curved sides, inner/outer diameters or distributed around the circumference.
True Radial Rings vs. Multipole Rings
A true two-pole radial ring and a multipole ring are also different concepts. A simple true-radial ring has one polarity on one circumference and the opposite polarity on the other. A multipole ring has several alternating poles around a circumference or face, depending on the design.
Multipole patterns are common in encoders, commutation, motors and specialized sensors. Use the Multipole Ring Visualizer to explore how changing pole count and orientation changes the field pattern.
True Radial Rings vs. Segmented Arc Magnets
A motor rotor assembled from individually magnetized arc segments can be designed to approximate a radial field, but that is not automatically the same as a one-piece true-radial ring. Each arc segment may have its own straight magnetization direction, while a true radial ring has a continuously changing local magnetization direction around the circumference.
The engineering choice depends on torque target, pole count, air gap, rotor diameter, magnet material, assembly method, retention system, cost and manufacturability.
For broader motor design context, see How Magnets Work in Electric Motors.
Which Magnetization Direction Is Best for a Rotary Sensor?
For many single-turn angular-position sensors, a diametrically magnetized disc, cylinder or ring is a common choice because the field vector rotates as the shaft rotates. Multipole rings may be preferred when the system needs incremental position information, repeated pole transitions or a different sensing architecture.
The correct choice depends on the sensor technology, required field magnitude, working gap, allowed angular error, mechanical tolerances and whether nearby ferromagnetic material distorts the field.
Which Magnetization Direction Is Best for a Motor or Magnetic Bearing?
There is no universal answer. Motor topology determines the required field orientation. Surface-mounted permanent-magnet rotors may use arc segments or specialized rings; some compact motors benefit from multipole or radial ring solutions. Interior permanent-magnet machines use a very different magnet arrangement.
Magnetic-bearing systems add another requirement: stability. Permanent magnets can carry or offload radial or axial load, but a passive permanent-magnet arrangement cannot provide stable static equilibrium in every degree of freedom without an additional constraint or stabilization method. See Magnets for Magnetic Levitation & Bearings for Earnshaw’s theorem, passive bearings, Halbach arrays, working-gap effects and stabilization options.
Instead of selecting magnetization by shape alone, start with the required air-gap field, pole count, rotor/stator or bearing geometry, force/stiffness target, temperature and demagnetization margin.
What to Put on a Magnet Drawing or RFQ
| Requirement | What to specify |
|---|---|
| Geometry | OD, ID, thickness, diameter, length and dimensional tolerances |
| Material | NdFeB, SmCo, ferrite or other material |
| Grade | Grade and coercivity class where required |
| Magnetization | Axial, diametric, true radial, multipole or drawing-defined pattern |
| Pole pattern | Pole count, pole pitch, indexing or orientation datum where applicable |
| Coating | Ni-Cu-Ni, epoxy or application-specific finish |
| Temperature | Continuous and maximum operating temperature |
| Magnetic output | Field, flux, sensor threshold, torque, force/stiffness or other functional requirement at a defined condition |
| Inspection | Dimensional and magnetic test methods plus acceptance criteria |
Use the Magnet RFQ Builder to submit a custom radial, diametric or multipole requirement. For material selection, use the Neodymium Magnet Grade Chart and Magnet Material Comparison.
Frequently Asked Questions
What is a diametric magnet?
A diametric magnet is a round magnet magnetized across one diameter, with north and south poles on opposite sides of its curved surface.
What is a radial magnet?
A true radial magnet is generally an annular magnet whose local magnetization direction follows the radius. In a simple two-pole ring, the inner and outer circumferences have opposite polarity.
Is a radial magnet the same as a ring magnet?
No. Ring describes shape; radial describes magnetization direction. Many stock ring magnets are axially magnetized.
Is diametric magnetization the same as multipole magnetization?
No. Diametric magnetization normally creates one north pole and one south pole across a diameter. Multipole magnetization creates several alternating poles.
Can a ring magnet be axial?
Yes. In fact, many stock ring magnets are axially magnetized, with poles on the two flat annular faces.
