Category: Magnet Tech

Permanent magnets are essential in countless applications — from motors, loudspeakers, and MRI machines to fridge magnets and magnetic tools. What makes them remarkable is their ability to retain magnetism for decades or even centuries. But why can they “remember” their magnetism so well, while other metals lose it instantly?

To understand this, we first need to explore the different types of magnetic materials, how they are classified, and the physical principles that allow permanent magnets to resist demagnetization.

1. Magnetic Material Classification: Hard vs. Soft Magnetic Materials

Magnetic materials can be broadly divided into permanent (hard) and soft magnetic materials based on their ability to retain magnetism.

Type	Coercivity	Key Feature	Example Materials	Applications
Permanent (Hard) Magnetic Materials	High (hundreds to thousands of kA/m)	Retain magnetism for long periods	Neodymium (NdFeB), Samarium Cobalt (SmCo), Ferrite, Alnico	Motors, generators, sensors, magnetic locks
Soft Magnetic Materials	Low (few A/m to tens of A/m)	Easily magnetized and demagnetized	Pure iron, silicon steel, permalloy	Transformers, inductors, electromagnets

Key Difference: Coercivity

• Coercivity is the measure of a material’s resistance to losing its magnetism when an opposing magnetic field is applied.
• Permanent magnets have high coercivity, meaning it takes a very strong reverse field to demagnetize them.
• Soft magnets have low coercivity, which makes them ideal for applications requiring rapid magnetization and demagnetization cycles.

2. Why Permanent Magnets Stay Magnetic

(1) High Coercivity – Resistance to Reverse Fields

Permanent magnets are made from materials whose atomic structure and chemical composition give them very high coercivity.
Example:

• Neodymium magnets can have coercivity values exceeding 1000 kA/m.
• In everyday life, typical stray magnetic fields are far too weak to affect them.

(2) Stable Magnetic Domain Alignment

Inside a magnetic material, tiny regions called magnetic domains each act like a small magnet.

• In permanent magnets, these domains are “locked” in one direction during manufacturing.
• This alignment is held in place by magnetic anisotropy — a property that makes certain crystal orientations energetically more favorable.

In contrast, in soft magnets, domains can shift or flip easily under even weak opposing fields.

(3) High Curie Temperature – Thermal Stability

The Curie temperature is the point at which a magnet loses its magnetic order due to heat.

• Alnico: 750–860 °C (1382–1580 °F)
• Ferrite: ~450 °C (842 °F)
• NdFeB: ~310 °C (590 °F)

Below this temperature, the atomic magnetic moments remain aligned. The higher the Curie temperature, the better the magnet resists thermal demagnetization.

(4) Optimized Microstructure

Modern permanent magnets are engineered to trap magnetic domains in place:

• Fine-grained crystals reduce the movement of domain walls.
• Grain boundary phases act as barriers against demagnetization.
• Example: Nd₂Fe₁₄B crystals in neodymium magnets are surrounded by Nd-rich grain boundaries that block reversal of domain alignment.

(5) Resistance to Environmental Factors

While permanent magnets are stable, they can lose magnetism due to:

• Corrosion (especially NdFeB, which requires nickel or epoxy coating)
• Severe mechanical shock
• Exposure to very strong reverse magnetic fields

With proper coating, handling, and storage, high-quality permanent magnets can maintain over 95% of their original magnetism even after decades.

3. How to Separate Permanent Magnets from Soft Magnetic Materials

In industrial and laboratory settings, distinguishing between permanent magnets and soft magnetic materials is important:

Method	Observation
Check Retentivity	After removing from a magnetizing field, a permanent magnet keeps strong magnetism; soft magnet loses it quickly.
Coercivity Testing	Apply a reverse field and measure the demagnetizing force needed.
Magnet Pull Test	Compare the holding force before and after exposure to opposing fields.
Material Identification	Use chemical composition analysis (NdFeB, SmCo, Alnico = hard; pure Fe, permalloy = soft).

4. The Science Behind Coercivity

Coercivity depends on:

• Magnetocrystalline anisotropy – Atomic lattice prefers specific spin directions.
• Microstructural defects – Can either pin domain walls (in hard magnets) or allow free movement (in soft magnets).
• Chemical composition – Elements like cobalt, rare earths, and aluminum increase coercivity.

High coercivity means a magnet “remembers” its original magnetization, making it resistant to accidental demagnetization from environmental fields or minor shocks.

5. Summary

Permanent magnets remain magnetic because:

• They have high coercivity, resisting reverse fields.
• Their magnetic domains are strongly locked in place.
• They have a high Curie temperature, resisting thermal effects.
• Their microstructure is optimized for stability.
• They are protected from corrosion and mechanical damage.

By contrast, soft magnetic materials are designed to switch magnetism on and off easily, making them ideal for electromagnets and transformer cores — but not for long-term magnetic retention.

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If you need expert advice on choosing the right magnet — whether high-coercivity permanent magnets for motors, or soft magnetic cores for transformers — feel free to contact us. Our engineering team can provide both technical guidance and customized magnet solutions.

In the world of permanent magnets, protecting the magnetic material from corrosion, wear, and environmental damage is essential. Traditionally, Ni-plating or Ni-Cu-Ni plating has been the go-to solution for surface protection, especially for neodymium (NdFeB) magnets. However, a newer technology—PVD (Physical Vapor Deposition) coating—is gaining attention as a high-performance alternative.

What is PVD Coating?

PVD coating is a vacuum-based surface treatment in which thin films of metals, nitrides, carbides, or other compounds are deposited onto a magnet’s surface in vapor form. Common PVD coatings for magnets include TiN (Titanium Nitride), CrN (Chromium Nitride), or multi-layer combinations. The process is done in a controlled chamber, ensuring uniform coating thickness and strong adhesion.

Advantages of PVD Coating for Magnets

1. Superior Hardness & Wear Resistance
   • PVD coatings typically have a hardness of 2,000–3,000 HV, far exceeding that of Ni plating (~500 HV).
   • Excellent for magnets used in high-friction or mechanical contact environments.
2. Excellent Corrosion Resistance
   • In many cases, PVD coatings outperform Ni-Cu-Ni plating in salt spray tests.
   • Resistant to moisture, sweat, and many chemicals.
3. Thin Yet Durable
   • Coating thickness is often 1–5 μm, so magnetic performance loss is minimal compared to thicker coatings.
4. Environmentally Friendly Process
   • No toxic electroplating chemicals; minimal waste.
5. Aesthetic Appeal
   • Can achieve colors like gold, black, rainbow, or metallic finishes—ideal for visible or decorative magnet applications.

Disadvantages & Considerations

• Higher Cost – PVD requires specialized equipment and longer processing time, making it more expensive than traditional plating.
• Line-of-Sight Limitation – Since the process is directional, complex shapes may have coating shadows or require rotation during deposition.
• Surface Preparation Critical – Magnets must be polished and cleaned thoroughly before coating; otherwise adhesion suffers.
• Less Common for Bulk Low-Cost Magnets – Best suited for applications where performance or appearance justifies the cost.

Why Use PVD Coating for Magnets?

PVD coating is especially attractive in:

• Medical devices (non-toxic, corrosion-proof, wear-resistant)
• Consumer electronics (decorative & functional)
• Luxury goods & watches (premium finish with durability)
• Motors & mechanical assemblies (abrasion resistance)
• Marine or humid environments (enhanced corrosion resistance)

PVD Coating vs. Ni-Plating / Ni-Cu-Ni Plating

Feature	PVD Coating	Ni Plating	Ni-Cu-Ni Plating
Hardness	★★★★★ (2000–3000 HV)	★★☆☆☆ (~500 HV)	★★☆☆☆ (~500 HV)
Corrosion Resistance	★★★★☆	★★★☆☆	★★★★☆
Thickness	1–5 μm	10–20 μm	15–25 μm
Magnetic Loss	Very Low	Low	Low
Appearance	Multiple colors & metallic effects	Silvery finish	Silvery finish
Cost	High	Low	Moderate
Environmental Impact	Eco-friendly	Uses chemicals	Uses chemicals

Conclusion

While Ni and Ni-Cu-Ni plating remain reliable and cost-effective choices for many magnet applications, PVD coating offers unmatched hardness, wear resistance, and decorative flexibility. For industries where performance, durability, or aesthetics are critical, PVD-coated magnets are a modern, premium solution worth considering.

If you’re looking for magnets with advanced PVD coatings, our team can provide customized options tailored to your application needs.

In the world of permanent magnets, new materials don’t appear very often. For decades, NdFeB (Neodymium Iron Boron) and SmCo (Samarium Cobalt) have dominated the high-performance magnet market. But in recent years, a promising newcomer—Samarium Iron Nitride (SmFeN)—has been gaining attention for its unique combination of high magnetic performance, corrosion resistance, and thermal stability.

SmFeN magnets are seen as one of the most exciting developments in the rare earth magnet field since the 1980s. Let’s explore their origin, how they’re made, how they compare to NdFeB, and what the future may hold.

A Brief History of SmFeN Magnets

The Sm–Fe–N magnetic compound was first studied in the late 1980s and early 1990s, when researchers discovered that introducing nitrogen into the Sm₂Fe₁₇ lattice could significantly increase its saturation magnetization and anisotropy field.

• 1980s: Sm₂Fe₁₇ compound known, but magnetic properties not competitive with NdFeB.
• 1991: Breakthrough nitrogenation process developed—leading to Sm₂Fe₁₇N₃.
• 1990s–2000s: Lab-scale synthesis proved high coercivity and good corrosion resistance.
• 2010s onward: Industrial interest grew due to Nd price volatility and demand for high-temperature magnets without heavy reliance on dysprosium.

Production Process of SmFeN Magnets

Manufacturing SmFeN magnets involves more steps than traditional NdFeB, mainly due to the nitrogenation process:

1. Alloy Preparation
   • Samarium and iron are alloyed (often via strip casting or gas atomization) to produce Sm₂Fe₁₇ powder.
2. Nitrogenation
   • The alloy powder is heated under high-purity nitrogen gas at around 500–600 °C.
   • Nitrogen atoms diffuse into the lattice, forming Sm₂Fe₁₇Nₓ (typically x ≈ 3).
   • This step enhances anisotropy and remanence without significantly reducing Curie temperature.
3. Powder Handling
   • Because the nitrogenated powder is prone to decomposition at high temperatures, low-temperature processing is critical.
4. Magnet Formation
   • Bonded magnets: SmFeN powder is mixed with polymer binders and formed via compression or injection molding.
   • Sintered magnets: More challenging due to nitrogen loss during sintering; research continues to improve this step.
5. Coating / Protection
   • Although corrosion resistance is better than NdFeB, coatings (epoxy, PVD, etc.) are often applied for harsh environments.

SmFeN vs. NdFeB: Key Comparisons

Property	SmFeN	NdFeB
Maximum Energy Product (BHmax)	~30–40 MGOe (bonded), higher in research samples	35–55 MGOe (sintered)
Temperature Stability	Excellent, retains magnetism above 200 °C	Standard grades lose strength above 80–120 °C; high-temp grades require Dy/Tb
Corrosion Resistance	Good, less prone to oxidation	Poor without coating
Raw Material Supply Risk	Samarium supply more stable; less dependence on heavy rare earths	Heavy reliance on Nd, Dy, Tb, prone to price volatility
Manufacturing Maturity	Emerging, still developing sintering process	Fully mature industrial production
Cost	Currently higher for small volumes due to limited production	Economies of scale make NdFeB cheaper

Advantages of SmFeN Magnets

• High temperature stability without expensive dysprosium additions.
• Good corrosion resistance, even without heavy coatings.
• Stable raw material supply, especially compared to dysprosium-heavy NdFeB.
• Low eddy current loss, making them ideal for high-frequency motors.

Disadvantages

• Lower peak energy product compared to the strongest NdFeB grades (today).
• Manufacturing challenges for sintered forms due to nitrogen loss at high temperatures.
• Less mature industrial chain, meaning higher costs for now.
• Mechanical fragility in some bonded forms.

Development Trends and Future Outlook

SmFeN magnets are currently most common in bonded magnet applications, such as high-speed motors, automotive sensors, and electronics, where their stability and corrosion resistance are valued. However, the holy grail is sintered SmFeN magnets—which could rival or surpass NdFeB in certain applications without relying on heavy rare earths.

Ongoing R&D is focused on:

• Low-temperature sintering techniques to prevent nitrogen loss.
• Hybrid magnets combining SmFeN with NdFeB for balanced performance.
• Scaling production to reduce costs.

With electric vehicles, wind turbines, and high-efficiency industrial motors demanding magnets that can handle heat, corrosion, and price volatility, SmFeN could become a major player in the next decade.

Conclusion

SmFeN magnets are not just another laboratory curiosity—they represent a strategic alternative to NdFeB, especially in applications where temperature stability and supply security matter most. While production challenges remain, ongoing research and the global push for rare-earth diversification could make SmFeN magnets one of the defining magnetic materials of the future.

In magnetic applications, one of the most critical factors in magnet selection is the air gap.

What is an Air Gap?

In magnet design and applications, the air gap refers to the non-magnetic separation between two components in a magnetic circuit. While the term “air” suggests empty space, the gap can also be filled with non-magnetic materials such as plastic, rubber, wood, coatings, or nickel plating.

Since these materials have very low magnetic permeability (close to that of air), they do not conduct magnetic flux. This creates higher reluctance (magnetic resistance) in the circuit, which reduces the effective magnetic flux density (B) reaching the target area. In practice, the larger the air gap, the weaker the magnetic field strength that can be achieved.

Interestingly, while large air gaps are often a challenge, in some designs—such as electric motors, transformers, or magnetic sensors—air gaps are intentionally introduced to control flux, prevent saturation, or fine-tune performance.

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How Air Gap Influences Magnet Selection

1. Choosing the Right Magnet Material

• AlNiCo Magnets
  AlNiCo magnets are valued for their excellent temperature stability. They perform reliably in applications that involve both air gaps and high operating temperatures.
  Example: industrial sensors operating in extreme heat.
• Ferrite Magnets
  Ferrite magnets are cost-effective and chemically stable. They are suitable when the air gap is very small and only a moderate magnetic field is required.
  Example: small DC toy motors where cost control is critical.
• Neodymium Magnets (NdFeB)
  NdFeB magnets are the strongest permanent magnets available today. They are the best choice when the air gap is relatively large and a powerful magnetic field is necessary.
  Example: magnetic separators, magnetic couplings, and levitation devices, where strong flux density across a gap is required.

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2. Effects on Magnet Size and Shape

• Magnet Size
  A larger air gap typically requires a bigger magnet to compensate for flux loss and maintain field strength.
• Magnet Shape
  Complex or non-uniform air gaps may require custom magnet geometries (arc segments, rings, or multi-pole assemblies) to optimize the circuit and maximize flux efficiency.

At HSMagnet, we specialize in custom magnet manufacturing to help engineers overcome these design challenges.

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3. Impact on Magnet Performance Requirements

• Magnetic Field Strength
  Bigger air gaps weaken the magnetic field. Stronger magnets with higher remanence are needed to achieve performance.
• Magnetic Permeability
  Using soft magnetic materials (e.g., iron or laminated steel) in the circuit helps guide and concentrate flux, reducing losses across the gap.
• Coercivity
  In designs with large air gaps or harsh conditions, magnets are more prone to demagnetization. High-coercivity materials such as NdFeB with special grades are essential for stability.

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Conclusion

The air gap is a critical factor in magnet design. Larger air gaps reduce magnetic strength, requiring careful selection of magnet material, size, shape, and circuit design to ensure performance.

Whether you choose AlNiCo for high-temperature reliability, ferrite for cost-effective designs, or NdFeB for maximum strength, understanding how air gaps influence magnet performance leads to greater efficiency, stability, and cost-effectiveness in your application.

👉 If you are an engineer, OEM, or industrial buyer, HSMagnet offers high-performance magnets and custom solutions to help you optimize designs for applications involving air gaps.

When considering permanent magnets for projects involving water, a common question arises: Will they rust? The answer depends on the magnet’s material, its protective coating, and the conditions of exposure.

Magnet Materials and Corrosion

Permanent magnets, such as neodymium (NdFeB), ferrite (ceramic), samarium cobalt (SmCo), and alnico, have varying levels of susceptibility to rust:

• Neodymium Magnets: These powerful magnets are highly prone to corrosion. Made from an alloy of neodymium, iron, and boron, they can rust quickly when exposed to water if their protective coating (typically nickel, zinc, or epoxy) is scratched or worn.
• Ferrite Magnets: Also known as ceramic magnets, these are more resistant to corrosion than neodymium but can still degrade in prolonged wet or humid environments.
• Samarium Cobalt and Alnico: These magnets are more corrosion-resistant due to their composition, but they’re not entirely immune, especially in salty or acidic water.

The Role of Coatings

Most commercial magnets come with protective coatings to combat moisture. Common coatings include:

• Nickel (Ni-Cu-Ni): A durable, multi-layered coating that provides good protection but can fail if damaged.
• Epoxy: Offers excellent water resistance but is less durable against physical wear.
• Zinc or Plastic: Used for specific applications, these provide varying degrees of protection.

If the coating is compromised, water can penetrate and cause rust, particularly in iron-based magnets like neodymium. Rust weakens the magnet’s structure and can reduce its magnetic strength over time.

Tips to Prevent Rust

To ensure your magnets withstand water exposure:

1. Choose the Right Magnet: Opt for ferrite or samarium cobalt magnets for better corrosion resistance in wet environments.
2. Inspect Coatings: Ensure the magnet’s coating is intact before use.
3. Apply Additional Protection: Use sealants, waterproof enclosures, or plastic coatings for added defense.
4. Dry Thoroughly: If exposed to water, dry magnets immediately to minimize corrosion risk.
5. Avoid Harsh Conditions: Saltwater or acidic environments accelerate rusting, so take extra precautions in such settings.

Conclusion

Permanent magnets can rust when exposed to water, especially if they’re uncoated or their protective layer is damaged. By selecting the right magnet type and ensuring proper protection, you can extend their lifespan and maintain performance in water-related applications. For advice on choosing the best magnets for your project, contact us!

Magnets are everywhere in our daily lives—from the speakers in your headphones to the motors in electric vehicles. But not all magnets are created equal. Among the key distinctions in magnet types are isotropic and anisotropic magnets. These terms refer to how the magnetic properties behave in different directions. In this blog post, we’ll break down what isotropic and anisotropic mean, explore their differences in production processes and magnetization, and discuss their practical uses. Whether you’re a hobbyist, engineer, or just curious, let’s dive in!

What Are Isotropic and Anisotropic Magnets?

To start, let’s define these concepts simply.

• Isotropic Magnets: The term “isotropic” comes from Greek roots meaning “equal in all directions.” In magnets, this means the magnetic properties—such as strength and the ability to be magnetized—are uniform regardless of the direction. You can think of it like a sphere: no matter which way you turn it, it behaves the same. Common examples include certain ferrite or alnico magnets that haven’t been specially aligned during manufacturing.
• Anisotropic Magnets: On the flip side, “anisotropic” means “different in different directions.” These magnets have a preferred axis or direction where their magnetic properties are strongest. Outside of that direction, the magnetism is weaker. This alignment makes them more efficient for specific applications. Neodymium (NdFeB) and samarium-cobalt (SmCo) magnets are often anisotropic.

In essence, isotropic magnets are versatile but less powerful in any one direction, while anisotropic ones are like specialized tools—optimized for performance along a particular path.

Differences in Production Processes

The way these magnets are made plays a huge role in their final properties. Here’s how the processes differ:

• Isotropic Magnets Production: These are typically produced without any external magnetic field during the key stages. The raw materials (like powdered metals or ceramics) are mixed, pressed into shape, and then sintered (heated to fuse particles) or cast. Since there’s no alignment force, the magnetic domains (tiny regions within the material that act like mini-magnets) point randomly in all directions. This results in even properties but lower overall magnetic strength. Common methods include dry pressing or injection molding for materials like isotropic ferrites.
• Anisotropic Magnets Production: The magic happens with the application of a strong external magnetic field during pressing or sintering. This field aligns the magnetic domains in a preferred direction as the material solidifies. For instance, in anisotropic ferrite magnets, the powder is pressed in a magnetic field, creating a “texture” where domains line up. For rare-earth magnets like NdFeB, the process might involve melt-spinning or hot deformation to enhance alignment. This extra step makes production more complex and often costlier, but it boosts the magnet’s energy product (a measure of strength).

Overall, isotropic production is simpler and cheaper, ideal for mass production, while anisotropic requires precise control for superior performance.

Differences in Magnetization

Magnetization is the process of turning a material into a magnet by exposing it to a magnetic field. Here’s where the isotropic-anisotropic divide shines:

• Isotropic Magnetization: These magnets can be magnetized in any direction after production because their domains aren’t pre-aligned. You apply a magnetic field, and the domains reorient freely. However, the resulting magnet is generally weaker, with a lower remanence (the magnetism left after the field is removed) and coercivity (resistance to demagnetization). They’re often multi-pole magnetized for applications needing complex patterns.
• Anisotropic Magnetization: These must be magnetized along their preferred axis to achieve maximum strength. Trying to magnetize them in other directions yields poor results because the domains are locked in place. This leads to higher remanence and coercivity—up to several times stronger than isotropic counterparts. For example, an anisotropic NdFeB magnet can have a magnetic energy product over 50 MGOe, compared to under 10 MGOe for isotropic versions.

In short, isotropic magnets offer flexibility in magnetization direction but at the cost of power, while anisotropic ones demand directional precision for peak efficiency.

Practical Usage and Applications

Choosing between isotropic and anisotropic magnets depends on the job at hand. Here’s a quick comparison:

Aspect	Isotropic Magnets	Anisotropic Magnets
Strength	Lower (e.g., 1-5 MGOe for ferrites)	Higher (e.g., 30-50 MGOe for NdFeB)
Directionality	Any direction	Preferred axis only
Cost	Cheaper	More expensive
Common Uses	Holding magnets, sensors, educational kits, fridge magnets	Electric motors, speakers, MRI machines, wind turbines

• Isotropic Uses: Their uniformity makes them great for applications where direction isn’t critical or where multi-directional magnetization is needed. You’ll find them in magnetic separators, loudspeakers (for less demanding audio), or even toys. They’re also preferred in environments with varying magnetic fields, like some automotive sensors.
• Anisotropic Uses: These powerhouses excel in high-performance scenarios requiring strong, directed magnetism. They’re essential in electric vehicle motors (for efficiency), hard disk drives (for data storage), and medical devices like pacemakers. In renewable energy, anisotropic magnets boost the output of generators in wind and hydro systems.

Wrapping It Up

Isotropic and anisotropic magnets represent two sides of the magnetic coin: one for versatility and affordability, the other for power and precision. Understanding these differences can help you pick the right magnet for your project or appreciate the tech in everyday gadgets. If you’re experimenting with magnets, start with isotropic ones for ease, then graduate to anisotropic for advanced builds.

What are your thoughts? Have you worked with these magnets before? Drop a comment below—I’d love to hear your experiences!

Note: This post is for informational purposes. Always consult technical specs for specific applications.

Magnetic filtration, also known as magnetic separation, is a process designed to remove ferrous contaminants from liquids, coolants, and slurries. The fluid flows around a high-intensity magnetic core or rod, and ferrous particles are drawn out of the stream and held in a magnetic trap. Once full, the filter can be cleaned and reused, providing a sustainable and cost-effective solution for industrial fluid management.

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Permanent magnets are the backbone of modern industries, from medical imaging to renewable energy. However, their performance is not defined solely by magnetic strength—corrosion resistance is equally critical. Iron, the key element behind strong ferromagnetic properties, is also highly reactive with moisture, making many high-performance magnets vulnerable to degradation if not properly protected.

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Magnets are often listed with values such as surface Gauss, remanence (Br), and pull strength. While these terms are related, they describe different aspects of a magnet’s performance. Understanding their distinctions is critical for engineers, buyers, and anyone selecting magnets for industrial or commercial applications.

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Permanent magnet materials must undergo rigorous testing to ensure their performance, consistency, and suitability for industrial applications. Several standardized methods exist to evaluate flux density, total flux, and magnetic hysteresis characteristics. Below is an overview of the most widely used testing techniques.

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