In high-efficiency power electronics, the core material isn’t a minor detail—it largely determines how low your losses can realistically go.

Pick the wrong soft magnetic material, and you’ll feel it in efficiency, size, and thermal load. Among the common options, amorphous metals tend to stand out when the goal is simply to reduce core loss as much as possible.

Amorphous low-loss magnetic cores manufactured by Hongwang

Key Points

Amorphous metals (often called metallic glasses) are widely used in applications where core loss needs to be kept very low, especially in always-on equipment like distribution transformers.
Their performance mainly comes from a random, non-crystalline atomic structure. This structure helps reduce both hysteresis loss and eddy current loss.
Amorphous cores work much better than traditional silicon steel. This is especially true in transformers that are always on.
The main downside is a higher upfront material cost, though in many cases it is offset over time through energy savings.

Why Amorphous Metals Work Great as a Soft Magnetic Material

Amorphous metals are often called metallic glasses. They are built to cut energy loss in magnetic devices. What really makes them work is their non-crystalline atomic structure — closer to glass than conventional metals.

This structure directly affects both main sources of core loss: hysteresis and eddy currents. It’s not a tweak at the design level; it’s baked into the material itself. That’s why they’re often the go-to option when efficiency is the priority.

Understanding the Problem: What is Core Loss in Magnetic Parts?

Core loss is the energy a magnetic component dissipates as heat under a changing magnetic field, including in transformers, motors, and inductors. In transformers, this includes the energy consumed while the unit remains energized but unloaded.

Core loss is a key design concern for engineers. Understanding where it comes from is the first step to reducing it. According to experts on soft magnetic materials, there are two main types of core loss:

Hysteresis Loss: This is the energy needed to flip the tiny magnetic zones inside the material back and forth. It can be loosely thought of as a form of internal magnetic resistance, although in practice it’s tied to how easily domains can reorient. This loss relates directly to a property called coercivity. Materials with lower coercivity require less energy to reverse their magnetic direction.
Eddy Current Loss: These are small, circular electric currents that flow within the core itself. The changing magnetic field creates them. They generate heat, similar to a heating element. This loss depends on the material's electrical resistance and thickness.

The Amorphous Advantage: How Atomic Structure Cuts Core Loss

The secret to low core loss in amorphous metals is their atomic structure. Unlike regular metals, their atoms are arranged randomly. This "disorder" is created by cooling the molten metal alloy very fast. There is not enough time for crystals to form.

This unique structure gives amorphous metals two powerful advantages in the fight against energy loss.

Fighting Hysteresis Loss with Low Coercivity

In standard crystal materials like silicon steel, atoms form a neat, repeating pattern. This pattern creates "easy" and "hard" directions for the magnetic field to follow. In crystalline materials like silicon steel, grain boundaries and preferred directions make it harder for magnetic domains to move. They act as obstacles to domain movement.

Amorphous metals have no crystal patterns or grain boundaries. Their random structure means there are no roadblocks and no preferred directions. Magnetic domains can move and reorient with much less resistance.

Amorphous alloys are also produced as very thin ribbons. This thin ribbon form limits the path available for circulating currents, keeping eddy current loss much lower than in conventional laminated steels.

Fighting Eddy Currents with High Resistivity

The specific elements used to make amorphous alloys give them high electrical resistivity. Elements like silicon and boron do this. This property makes it much harder for electricity to flow through the material.

Higher resistivity makes it harder for these currents to form and circulate.

Also, amorphous metals are made as very thin ribbons. The thin ribbon form further limits the scale of eddy currents. Combined with the ribbon-like geometry, eddy current loss is kept much lower than in conventional laminated steels.

amorphous ribbons produced by HWHG

Amorphous Metals vs. Traditional Materials: A Direct Comparison

Beyond theory, a direct comparison helps illustrate the practical differences. The table below compares key performance numbers for amorphous metal, silicon steel, and ferrite. These figures help explain why amorphous metals are often preferred in low-loss designs.

Property	Amorphous Metal	Grain-Oriented Silicon Steel	MnZn Ferrite
Core Loss (at 50/60 Hz)	Very Low (~0.2 W/kg)	Low (~0.8 W/kg)	N/A (High Frequency Use)
Core Loss (at High Freq.)	Low	Very High	Very Low
Magnetic Permeability	Very High	High	High
Coercivity	Very Low (< 4 A/m)	Low (~20 A/m)	Low (~15 A/m)
Saturation Flux Density	High (~1.56 T)	Very High (~2.0 T)	Moderate (~0.5 T)
Electrical Resistivity	Very High (~130 µΩ-cm)	Moderate (~50 µΩ-cm)	Very High
Magnetostriction	Low	Moderate	Moderate to High

Looking at typical numbers, amorphous alloys sit in an interesting middle ground — much lower loss than silicon steel, while still maintaining relatively high flux density compared to ferrites. It is a versatile and powerful soft magnetic material.

Real-World Impact: Where Amorphous Metal Cores Power Modern Electronics

From a design perspective, the low core loss of amorphous metals makes them well suited to cores designed for lower magnetic loss. These materials are now widely used in practical applications.

High-Efficiency Distribution Transformers: These units remain connected to the grid around the clock, so no-load loss becomes a constant energy drain. Amorphous core material can reduce this standby loss substantially compared with older silicon steel designs, although engineers still need to consider whether the efficiency gain justifies the material trade-offs for a particular transformer.
Switched-Mode Power Supplies (SMPS): In the power supplies for our computers, servers, and phone chargers, efficiency is key. Amorphous cores keep low losses even at high switching frequencies. This allows us to design smaller, lighter power supplies that make less waste heat.
High-Frequency Inductors and Chokes: Parts in solar inverters, electric vehicle (EV) chargers, and industrial motors must handle high frequencies with minimal power loss. The superior magnetic permeability and low loss of amorphous metal make it the ideal choice for these critical uses. This improves overall system efficiency.

Conclusion: The Clear Choice for High-Efficiency Designs

If reducing core loss is the goal, material selection plays a major role. Amorphous metals provide a clear advantage. Their unique, disordered atomic structure gives them very low coercivity and high electrical resistivity.

This combination helps reduce both hysteresis and eddy current losses. In practice, this leads to lower total core loss compared to traditional materials, though the final choice still depends on design priorities. So in practice, it’s less about “better or worse” and more about where the trade-offs land for a given design.

Frequently Asked Questions (FAQ)

What is the main difference between amorphous and nanocrystalline soft magnetic materials?

Amorphous materials have a completely random, glass-like atomic structure. Nanocrystalline materials are made from amorphous ribbons that are heat-treated. This process creates tiny, nanometer-sized crystal grains. This gives them excellent high-frequency properties and often higher magnetic permeability. But they can be more expensive.

Are amorphous metal cores more expensive than silicon steel?

Yes, the initial cost of amorphous metal is higher than traditional silicon steel. This is due to a more complex making process. However, for many uses, the total cost over the product's lifetime is lower. This is because the big energy savings from reduced core loss quickly pay back the initial investment.

Why is low magnetostriction important for a core material?

Magnetostriction is a property that causes a material to slightly change its shape when a magnetic field is applied. This constant flexing can create an audible hum or buzz in transformers and inductors. A material with low magnetostriction, like amorphous metal, makes much less noise. This leads to quieter operation.

Does temperature affect the performance of amorphous cores?

Yes, all magnetic materials are affected by temperature. Amorphous metals perform well across a wide range of temperatures. As temperature increases, their saturation flux density tends to decrease slightly. Engineers must account for this effect when designing parts for high-temperature environments.

Can amorphous metals completely replace silicon steel?

Not entirely. While amorphous metals are better for low-frequency energy loss, the best grain-oriented silicon steels have higher saturation flux density. This means silicon steel can sometimes handle more magnetic flux in the same size core. For designs where maximum power density is the only goal and efficiency is less important, silicon steel may still be used.

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