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Magnetic Grades: Comprehensive Guide to Magnet Strength and Types

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Magnetic grades show how strong a magnet is and how it performs under certain conditions. Each grade is a measurable energy product, usually labeled as “N” with a number—N35, N52, and so on. These numbers mark the magnet’s maximum energy density in Mega-Gauss Oersteds (MGOe), generally between 30 and 55 for neodymium magnets.

These values help determine the magnetic force a material can deliver and how it reacts to heat, pressure, or demagnetizing fields. Magnets come in several material types—Neodymium (NdFeB), Samarium Cobalt (SmCo), Alnico, and Ferrite. Each has its own grade system and performance limits.

For example, SmCo magnets can operate at temperatures up to 350°C. Standard neodymium types lose magnetism above 80°C unless specifically rated as “H” or “SH.” Engineers need to match the magnetic grade to both strength and environmental requirements.

Magnetic Grades

Understanding Magnetic Grades

Magnetic grades define the measurable strength and thermal limits of permanent magnets. Each grade connects to specific physical properties like magnetic energy density, coercivity, and remanence.

Definition and Importance of Magnet Grades

A magnet grade shows the maximum energy product (BHmax) a material can provide, measured in Mega Gauss Oersteds (MGOe). This value measures how much magnetic energy the magnet can store per unit volume.

An N35 magnet has a BHmax of 35 MGOe. An N52 magnet reaches 52 MGOe. As BHmax increases, higher-grade magnets generate more magnetic flux in smaller sizes.

Grades also show thermal stability. Standard neodymium magnets (no suffix) work up to 80°C, while an N42SH grade can handle 150°C. This classification lets engineers pick materials that keep magnetization within their temperature limits.

Common magnet materials include NdFeB (neodymium-iron-boron), SmCo (samarium-cobalt), and Alnico. Each has different coercivity and remanence values, affecting resistance to demagnetizing forces or high temperatures.

How Magnet Grades Are Determined

Manufacturers grade magnets using standardized tests. They measure remanence (Br) in Gauss (G) or Tesla (T), coercivity (Hc) in Oersteds (Oe), and BHmax in MGOe.

A typical N35 magnet has a remanence of 11,700–12,200 G, coercivity of 10,800–11,500 Oe, and BHmax of 33–36 MGOe. A hysteresis loop tracer records the magnet’s response to an external magnetic field.

Neodymium magnets achieve higher grades than ceramic or Alnico types because of their high energy-to-mass ratio. However, neodymium’s performance drops faster with temperature. Manufacturers add elements like dysprosium to boost coercivity and thermal resistance in high-grade magnets.

Magnetic Properties and Measurement Units

Magnetic properties show how a magnet interacts with external fields and materials. The three main parameters are remanence (Br), coercivity (Hc), and maximum energy product (BHmax).

Property	Unit	Typical Range (Neodymium N35–N52)	Function
Br	Gauss (G)	11,700–14,800	Determines magnetic flux density
Hc	Oersted (Oe)	10,800–14,000	Measures resistance to demagnetization
BHmax	MGOe	33–52	Indicates total magnetic energy storage

BHmax combines Br and Hc, so a higher value means more magnetic energy per volume. An N52 magnet with 14,800 G Br and 14,000 Oe Hc produces dense magnetic fields, making it a good choice for compact motors or sensors.

Units like Gauss, Oersted, and MGOe allow direct comparison between magnet types and grades across industrial and scientific uses.

Magnetic Grades

Types of Magnetic Materials and Their Grades

Permanent magnets differ in composition, strength, and resistance to heat and demagnetization. Grades define properties like maximum energy product (BHmax), coercivity (Hci), and operating temperature range.

These factors shape how each type works in different environments.

Neodymium Magnet Grades

Neodymium magnets (NdFeB) are rare earth magnets made from neodymium, iron, and boron. Their grades run from N35 to N55, representing a BHmax of 30–55 MGOe. A higher grade brings more magnetic energy density—stronger fields for the same size.

These magnets work best below set temperatures. N52 magnets typically handle up to 80°C. Grades like N48H or N42SH can manage 120–150°C. The letter suffix (M, H, SH, UH, EH, TH) signals coercivity and max working temperature.

Neodymium magnets have high remanence (1.0–1.4 Tesla), so they create strong attraction in small designs.

Overheating or corrosion can ruin them, so manufacturers usually add nickel-copper-nickel coatings or epoxy layers.

Electric motors, speakers, and magnetic sensors use neodymium magnets for their high flux density. Maximum strength comes at the cost of thermal stability, so engineers balance grade and coercivity for each situation.

Samarium Cobalt Magnet Grades

Samarium cobalt (SmCo) magnets are another rare earth option. These magnets show BHmax values between 16 and 32 MGOe and keep their strength up to 350°C. Grades like SmCo 24 or Sm2Co17 32 define energy product and composition ratio.

SmCo magnets have intrinsic coercivity (Hci) of 600–2000 kA/m. That means they resist demagnetization from heat and outside magnetic fields. Using cobalt instead of iron gives them superior oxidation resistance, so they don’t need protective coatings.

Their crystal structure keeps magnetic alignment stable, even as temperatures change. Aerospace actuators, high-speed motors, and military sensors often rely on SmCo magnets.

SmCo magnets are brittle and expensive, though. Machining them is tough, and the price per kilogram is higher than NdFeB. Still, they work reliably where temperatures go over 200°C.

Alnico and Ferrite Magnet Grades

Alnico magnets mainly use aluminum, nickel, and cobalt. Common grades are Alnico 2, 5, and 8. Their BHmax ranges from 1.5 to 9 MGOe. Alnico magnets can operate from -250°C to 500°C without much loss in magnetism.

Alnico’s low coercivity (30–160 kA/m) makes them easy to demagnetize, but they offer great thermal stability.

Ferrite magnets, or ceramic magnets, are made from strontium or barium ferrite (SrFe12O19 or BaFe12O19). Grades like Y10, Y25, Y30, and Y35 show BHmax values between 1.1 and 4.0 MGOe.

Ferrite magnets resist corrosion and stay chemically stable, which is useful for outdoor or humid settings.

Alnico magnets go into instruments and sensors needing a linear magnetic response. Ferrite magnets are common in loudspeakers, refrigerator seals, and electric motors.

Ferrite magnets are cheap and corrosion-resistant but weak. Alnico magnets handle high temperatures but have lower coercivity.

Magnetic Grades

Factors Affecting Magnet Grades and Performance

Magnet grades depend on how materials react to heat, magnetic load, and environmental stress. Temperature limits, demagnetization resistance, and the intended use all play a role in how long a magnet keeps its rated strength.

Operating Temperature and Maximum Operating Temperature

Each magnet type has a set operating temperature range and maximum operating temperature (Tmax).

Standard neodymium (NdFeB) magnets work up to 80°C. High-temperature grades like N35EH can reach 200°C before losing magnetization.

When temperatures go past Tmax, coercivity (Hc) drops. That leads to partial or permanent demagnetization. Heat shakes up the alignment of magnetic domains that hold the field.

Different materials handle heat in their own ways. Samarium cobalt (SmCo) magnets stay stable up to 350°C. Ferrite (ceramic) magnets work between -40°C and 250°C. SmCo fits aerospace and high-speed motors. Ferrite fits outdoor or automotive sensors.

Demagnetization Resistance

Demagnetization resistance means the magnet can keep its magnetization under external fields, heat, or stress. This mostly depends on intrinsic coercivity (Hci), measured in kOe. N35 magnets have an Hci around 12 kOe. N52 magnets may hit 14 kOe.

A magnet with higher Hci stands up better to reverse magnetic fields. Motors and sensors often need this, since alternating fields can weaken low-coercivity materials. SmCo magnets with Hci up to 30 kOe hold their magnetization even under tough conditions.

Coatings like nickel-copper-nickel (NiCuNi) or epoxy don’t change coercivity. Instead, they protect the surface from corrosion and help keep magnetic performance steady.

Designers sometimes trade higher coercivity for lower remanence (Br). That means a magnet that resists demagnetization may put out a bit less flux density, but it’ll work more reliably in changing environments.

Application Considerations

Every magnet grade matches certain operating conditions based on energy product (BHmax), temperature tolerance, and mechanical properties.

N52 neodymium magnets (BHmax ≈ 52 MGOe) deliver strong pull in small designs but max out at 80°C.

Alnico 5 (BHmax ≈ 5.5 MGOe) works well up to 450°C, so it’s a better option for heat-exposed instrumentation.

For electric motors, engineers usually pick N42SH or N48H magnets with Tmax between 150–180°C to balance strength and heat resistance.

In magnetic separators, N42 or N45 grades reach surface flux of 4,000–6,000 gauss for efficient metal extraction.

SmCo magnets stay stable across wide temperature ranges and resist corrosion, making them a go-to for medical imaging or aerospace.

For consumer products, ferrite magnets (Y30–Y35) offer durability and keep costs down, especially in humid or outdoor settings.

Selecting the Right Magnetic Grade

Magnet grade selection comes down to measurable properties: magnetic energy density, temperature resistance, and cost per unit of magnetic strength.

Each grade’s design and composition directly shape how it performs in real-world environments.

Comparing Magnetic Grades for Applications

Magnetic grades set the amount of energy a magnet can store, measured as Maximum Energy Product (BHmax) in MGOe.

N35 magnets have about 35 MGOe; N52 magnets reach 52 MGOe, so they generate roughly 48% more magnetic energy in the same volume.

Nd₂Fe₁₄B (neodymium-iron-boron) gives magnets high strength but limits their temperature tolerance.

Standard grades handle up to 80°C, while N42SH or N48UH can manage 150°C–180°C thanks to tweaks in alloying and heat treatment.

Design geometry matters too. Thin or small magnets lose magnetization faster under heat or opposing fields.

Engineers often pick a slightly higher grade, like N45SH, to keep flux density up in compact builds.

Applications such as electric motors, sensors, and magnetic couplings rely on finding the right balance between strength and stability.

Cost vs. Performance

The price of neodymium magnets jumps with grade. N52 magnets can cost 70–100% more than N42 magnets but only give about 20% more strength.

Higher grades need tighter crystal alignment and rare-earth purity above 97% Nd content, which drives up costs.

Because of this, engineers usually reserve high grades for compact or weight-sensitive designs. N35–N42 magnets fit general uses where there’s space for larger magnets.

Using two N42 magnets instead of one N52 can get similar pull force at a lower price and with less brittleness.

The right grade is the one that minimizes total system cost without pushing thermal or structural limits.

Industry Standards and Grade Designations

Standardized designations like IEC 60404-8-1 and ISO 10004 define magnetic grades for permanent magnet materials.

The prefix “N” marks neodymium magnets, with the number showing BHmax. Suffix letters—M, H, SH, UH, EH, and AH—indicate max operating temperatures from 100°C to 230°C.

For example, N42H runs reliably up to 120°C. N52AH stands up to 230°C thanks to extra dysprosium (Dy) doping at 3–5%.

That element boosts coercivity, so magnets don’t demagnetize under high heat.

Manufacturers confirm these ratings with Gaussmeter testing and hysteresis loop analysis.

Consistent labeling keeps magnets interchangeable across suppliers and maintains predictable performance in regulated fields like aerospace (AS9100) and automotive (IATF 16949).

Standardization lets engineers match grades to design and environmental needs with confidence.

Frequently Asked Questions

Magnet grades reflect measurable qualities—magnetic energy, temperature resistance, and material composition. These traits shape performance in electronics, automotive, and medical gear.

What factors determine the strength of a magnet?

A magnet’s strength comes down to its maximum energy product (BH)max, measured in MGOe.
Neodymium magnets range from N35 (35 MGOe) to N52 (52 MGOe). A higher (BH)max means more magnetic energy per unit volume.
Material composition matters too. Neodymium-Iron-Boron (NdFeB) magnets produce stronger fields than ferrite magnets, thanks to their Nd2Fe14B crystalline structure.
Precise sintering boosts residual flux density, often between 1.2–1.4 Tesla.
Temperature stability sets the limit on usable strength. Standard N-grade magnets lose magnetization above 80 °C, but SH and UH grades keep working up to 150 °C and 180 °C.
Adding elements like dysprosium increases coercivity, so magnets resist demagnetization at high heat.

How are neodymium magnets classified by grade?

Neodymium magnets use a grade code: a letter and number, like N35, N42SH, or N52.
The number shows the (BH)max value in MGOe; suffix letters reveal temperature limits.
Grades without a suffix—N35 or N52—work up to 80 °C. Adding H, SH, UH, or EH raises the max working temperature to 120 °C, 150 °C, 180 °C, and 200 °C.
Manufacturers tweak the neodymium and dysprosium ratio in the alloy, raising intrinsic coercivity from about 10 kOe to 25 kOe.
This system lets engineers match strength and thermal stability to design needs, whether it’s a compact sensor or a high-heat motor.

What does the 'N' rating mean in magnet grades?

The “N” in a magnet grade shows it’s a neodymium-based magnet.
The number—like 35, 42, or 52—refers to maximum energy product (BH)max. That’s the amount of magnetic energy the material can store.
An N52 magnet with 52 MGOe generates a stronger field in a smaller size than an N35 magnet at 35 MGOe.
The difference comes from denser magnetic domain alignment inside the NdFeB lattice, which bumps remanence (Br) from 1.17 T to 1.42 T.
Higher N-ratings let smaller magnets match the pull force of bigger, lower-grade magnets—great for tight spaces.

How do different magnet grades compare in terms of power?

Power differences between grades show up in magnetic flux density and coercive force.
An N35 magnet usually gives a surface field of about 1.2 Tesla, while an N52 can hit 1.45 Tesla with the same size.
This extra power comes with trade-offs. N52 magnets demagnetize faster above 80 °C.
N35 or N42SH magnets stay stable at 120–150 °C thanks to higher dysprosium, which favors stability over raw power.
When sustained force in heat matters, engineers pick lower grades with higher coercivity instead of chasing the highest field strength.

What are the applications of different magnet grades?

N35–N42 magnets show up in general-purpose products: speakers, magnetic mounts, and small motors. These grades balance cost and output, working best below 100 °C.
N42SH–N52 grades go into compact or high-performance devices—think servo motors, precision actuators, and magnetic couplings. Their higher energy density supports torque in tight spaces.
N35EH or N38UH magnets handle up to 180–200 °C, so they’re good for automotive pumps or turbine sensors. The trade-off is less magnetic energy density—around 35–38 MGOe—due to more dysprosium for heat resistance.

How is the gauss value related to a magnet's grade?

The gauss value measures magnetic flux density right at a magnet’s surface. This value shows up in Gauss (G) or Tesla (T).
Gauss tells you how strong the field is at a certain spot, not how much energy the magnet holds overall.
Magnet grade gives the potential energy density, but the actual gauss reading changes with magnet size, shape, and configuration.
Take a 25 mm diameter N52 disc—it might hit 6,500 G at the surface. A bigger N42 block, thanks to its volume, could even top 7,000 G.
Design geometry and air gap spacing can shift how the flux spreads out. Engineers rely on both grade (MGOe) and measured gauss values to figure out what’ll happen in real magnetic assemblies.

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