Ferrite Core Material Properties Guide
The properties that define a ferrite material are initial permeability (µ), core loss vs frequency and flux swing, saturation flux density (Bs), resistivity, Curie temperature and the impedance curve. MnZn ferrite (µ 1000–15000, best below ~1 MHz) suits power; NiZn (µ 10–500, high resistivity) suits EMI and RF. Read all of them at your operating point — a datasheet number at one frequency is not the design value.
A ferrite material datasheet lists a dozen numbers, but three or four of them decide whether your transformer or inductor works. This guide explains each key property, the typical values for MnZn and NiZn, and how to use them in a real design.
1. Initial permeability (µ)
Permeability is how easily the material conducts magnetic flux. MnZn ferrite ranges from 1000 to 15000; NiZn from 10 to 500. Higher µ means more inductance per turn, but also more sensitivity to DC bias, temperature and frequency — the Permeability note explains the trade-offs in detail.
2. Core loss vs frequency and flux
Core loss (W/m³) rises steeply with frequency and flux swing. MnZn is lowest in the 100 kHz–1 MHz power window; NiZn wins above ~1 MHz thanks to high resistivity. Always read the loss curve at your switching frequency and ΔB — the Core Loss note shows the calculation method.
3. Saturation flux density (Bs)
Ferrite saturates at roughly 0.3–0.5 T, far below metal-powder cores. Keep the operating flux with margin under Bs at the worst-case current and temperature, because Bs falls as the core heats up. See the Saturation note for the full comparison.
4. Resistivity and impedance
MnZn resistivity is about 0.5–5 Ω·m; NiZn is orders of magnitude higher (10³–10⁶ Ω·m), which limits eddy-current loss at MHz. For EMI chokes, what matters is impedance — Z = 2πfL plus the resistive loss term — across the noise band. Pick the µ grade so impedance peaks where you need suppression.
5. Curie temperature
Ferrite loses its magnetic properties above the Curie point, typically 120–250°C depending on the grade. Permeability peaks near the Curie point and collapses just before it, so derate the design for the hottest ambient — the Temperature note covers this in depth.
Property reference
| Property | MnZn ferrite | NiZn ferrite |
|---|---|---|
| Permeability | 1000–15000 | 10–500 |
| Saturation Bs | ≈ 0.4–0.5 T | ≈ 0.25–0.35 T |
| Resistivity | 0.5–5 Ω·m | 10³–10⁶ Ω·m |
| Practical frequency | < ~1 MHz | 1–100 MHz+ |
| Typical use | Power transformers, inductors | EMI chokes, RF |
For real grade data, see the Technical Data tables, and the MnZn vs NiZn guide for the selection decision. YUTE supplies custom ferrite cores across both families with IATF 16949 quality management, plus AEC-Q200 stress testing per part number on request — send your frequency, power and size targets through the engineering RFQ for a free evaluation.
Frequently Asked Questions
What properties define a ferrite material?
Initial permeability, core loss versus frequency and flux swing, saturation flux density, resistivity, Curie temperature and the impedance curve. Together these describe how the material behaves in a given application.
Which property matters most for power conversion?
Core loss at the operating frequency and flux swing, because it determines how much heat the core generates and therefore often sets the size limit. Permeability then determines the turns needed, and saturation sets the flux ceiling.
Why does resistivity matter in ferrite?
Ferrite is a ceramic with high resistivity, which limits eddy-current loss inside the material. That is why ferrite remains usable at frequencies where metal cores would suffer prohibitive eddy-current loss.
How does temperature affect ferrite performance?
Saturation flux density falls as temperature rises, and core loss also varies with temperature in a material-specific way. Curie temperature marks the point where the material loses its magnetic properties entirely.
Should I compare ferrite grades at my operating point?
Yes. Grades optimised for different frequency bands can look similar on a summary page but diverge substantially at your actual frequency, flux swing and temperature, so compare loss curves under those conditions.
Verwandte Seiten
Unterstützung bei der Auswahl?
Senden Sie Arbeitspunkt und Bauraum — wir schlagen Kern und Wicklung vor.