Cartridge Magnets: Samarium Cobalt vs Neodymium

The role of the magnet in a phono cartridge

A phono cartridge is a tiny generator. It converts the movement of the stylus in the record groove into an electrical signal by moving a magnet (or a coil) within a magnetic field. The magnet's strength and shape directly affect how much voltage the cartridge produces for a given amount of stylus movement, which in turn defines the cartridge's output level.

Two types of rare earth magnets are common in modern cartridges: samarium cobalt and neodymium. Both belong to the same family of strong permanent magnets, but they differ in energy density, temperature behavior, and cost. These differences influence the cartridge's physical design, its compatibility with different phono stages, and its long-term consistency.

Samarium cobalt: the stable performer

Samarium cobalt magnets have been used in audio components for decades. They are known for their excellent temperature stability: their magnetic output remains nearly constant across a wide temperature range, and they are highly resistant to demagnetization. This makes them a favorite for cartridge manufacturers who want a consistent sound over many years, even in warm environments or under strong signal conditions.

The tradeoff is that samarium cobalt has a lower energy product than neodymium. To achieve the same magnetic flux, a samarium cobalt magnet must be physically larger. That can influence the cartridge's weight and its moving mass, which in turn affects tracking ability and compatibility with certain tonearms. However, cartridge designers often compensate with lighter cantilevers and optimized generator geometries.

Neodymium: high energy in a small package

Neodymium magnets are the strongest commercially available permanent magnets. Their high energy product allows cartridge designers to generate a powerful magnetic field with a very small magnet. This is especially useful for moving magnet cartridges, where the magnet moves with the stylus. A smaller, lighter magnet reduces the moving mass, which can improve tracking and transient response.

The main drawbacks of neodymium are its susceptibility to corrosion and its lower maximum operating temperature compared to samarium cobalt. Manufacturers typically coat neodymium magnets to prevent oxidation, and modern grades have improved thermal limits. For home use, these limitations are rarely a practical concern. The higher energy output often means a cartridge with neodymium can produce a stronger signal without additional amplification, which is convenient when connecting to a receiver or integrated amplifier.

Output strength and design tradeoffs

The choice of magnet material is one of several factors that determine a cartridge's output voltage. Other factors include the number of coil turns, the cantilever length, and the geometry of the magnetic circuit. A neodymium magnet can allow a smaller, lighter generator to reach the same output as a larger samarium cobalt assembly, but designers may also choose neodymium to push output higher.

Higher output is not always better. It can overload a phono stage if the gain is too high, leading to distortion. Conversely, lower output cartridges require more gain and can be more susceptible to hum and noise. The ideal output depends on the phono preamp's input sensitivity and the rest of your system. For a detailed look at how output level interacts with your gear, see the guide on cartridge output voltage.

The magnet's size and weight also affect the cartridge's compliance, which influences how well it pairs with your tonearm's effective mass. Low-compliance cartridges work best with heavy tonearms, while high-compliance cartridges suit lighter arms. The choice between samarium cobalt and neodymium can shift the cartridge's compliance, so it is worth checking the specifications. Learn more in the article on cartridge compliance match.

Which magnet matters for your setup

For most listeners, the magnet type is a secondary specification. The stylus shape, cantilever material, and overall cartridge design have a larger impact on sound quality. However, understanding the difference helps you interpret specifications and make an informed choice, especially if you are comparing cartridges for a specific tonearm or phono stage.

If you are looking for a cartridge that will maintain consistent performance in a room with temperature fluctuations, or if you plan to keep your turntable for many years, a samarium cobalt implementation is a safe choice. If you want a high-output cartridge that works well with a modest phono stage, neodymium is often the way to go, as it can deliver strong signal levels without extra gain stages.

You can find both magnet types across the price range. When shopping, focus on the cartridge's overall specifications and how they match your tonearm and phono preamp. The moving magnet vs moving coil cartridge guide explains the broader design differences, and the cartridge upgrade guide offers step-by-step advice for upgrading.

Caring for your cartridge

Regardless of the magnet type, a phono cartridge is a delicate component. The Library of Congress recommends keeping playback equipment clean and well maintained to ensure proper performance. This includes regularly inspecting the stylus tip, checking that the cartridge is correctly aligned, and ensuring that the tonearm's tracking force is set appropriately.

Keep your turntable in a clean, dry environment and avoid exposing it to strong magnetic fields, which can occasionally affect the generator. For more detailed advice on record and equipment care, see the turntable maintenance checklist and the turntable isolation guide.

What to pick for your use

Questions

Is a neodymium magnet cartridge automatically better than a samarium cobalt one?

No. Neodymium offers a higher energy product, which can allow a smaller and lighter magnet, but the overall cartridge design, stylus, and compliance matter more. Both types can sound excellent if properly engineered.

Does the magnet type affect the cartridge's output voltage?

Yes, indirectly. The magnet's strength influences the magnetic flux in the generator, which is a factor in output voltage. However, designers can adjust coil turns and other parameters to achieve a target output with either magnet type.

Are samarium cobalt magnets more durable?

Samarium cobalt is highly resistant to demagnetization and has excellent temperature stability. Neodymium requires a protective coating to prevent corrosion and has a lower maximum operating temperature, but modern grades are reliable for home use.

Should I choose a cartridge based on its magnet type?

No. Focus on the cartridge's compliance, stylus shape, output level, and how it matches your tonearm and phono preamp. The magnet type is a minor specification unless you have specific temperature or output requirements.

Can a neodymium magnet damage my records?

No. The magnet is inside the cartridge and does not come into contact with the record. The stylus is the only part that touches the groove, and its shape and tracking force determine record wear.