--- title: "Magnetisation: Diamagnetism, Paramagnetism and Ferromagnetism" description: "Matter in a magnetic field acquires a magnetisation of its own, weakly opposing the field, weakly aligning with it, or aligning strongly and staying that way. Ferromagnetic order comes from an interac" canonical: https://lightmysky.com/learn/science/magnetisation-diamagnetism-paramagnetism-and-ferromagnetism-mt_1apyQ1_1gg source: https://lightmysky.com/learn/science/magnetisation-diamagnetism-paramagnetism-and-ferromagnetism-mt_1apyQ1_1gg.md retrieved: 2026-09-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Magnetisation: Diamagnetism, Paramagnetism and Ferromagnetism Matter in a magnetic field acquires a magnetisation of its own, weakly opposing the field, weakly aligning with it, or aligning strongly and staying that way. Ferromagnetic order comes from an interaction between neighbouring moments and disappears above the Curie temperature. Subject: Science · Area: Electricity & Magnetism · Ages 20 to 21 Page: https://lightmysky.com/learn/science/magnetisation-diamagnetism-paramagnetism-and-ferromagnetism-mt_1apyQ1_1gg ## Ready when they can - Sorts materials by how their magnetisation responds to an applied field and gives the microscopic reason for each class - Explains why an iron core multiplies the field of a solenoid while a copper one does almost nothing - Reads a hysteresis loop and says what its area and its width cost in a transformer core ## Lesson: Oppose weakly, align weakly, lock strongly Sort matter by what its atomic moments do in a field. Diamagnets have no permanent moments, so the field induces a weak opposing response and they are gently repelled. Every material shows a trace of this. Paramagnets carry permanent but randomly aimed moments that partly line up, giving weak attraction that fades as heat jostles the alignment. Ferromagnets couple neighbouring moments into domains that snap into line together. Slip an iron core into a solenoid and the field leaps. The core domains align with the coil and add their own field on top, multiplying the response thousands of times. Copper shows almost no gain since it lacks that cooperative alignment. This is why motors, transformers, and lifting magnets build coils around iron or steel. Switch the current and an electromagnet field follows; a permanent magnet keeps its domains frozen. **Example.** You can magnetise a nail by stroking it one way with a magnet. Each stroke drags more domains into line, and lifting the magnet at the end of each stroke avoids undoing the work. Stroking back and forth at random does far less. Count the paper clips the nail now lifts, then drop or heat it and watch the strength fade as disorder scrambles the alignment. **Tip.** Ferromagnetic order dies above the Curie temperature, where heat wins and iron goes paramagnetic. Each trip around a hysteresis loop costs energy as heat, and the loop area measures that cost per cycle. Its width sets the field needed to demagnetise. Transformer cores flip constantly, so they use narrow loops that waste little. **Recap.** Diamagnets weakly oppose, paramagnets weakly align, and ferromagnets lock domains together until heat past the Curie point scrambles them. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Dielectrics and the Polarisation of Matter](https://lightmysky.com/learn/science/dielectrics-and-the-polarisation-of-matter-mt_OYRr_k3IW6) - [Ampere's Law: Wires, Solenoids and Toroids](https://lightmysky.com/learn/science/amperes-law-wires-solenoids-and-toroids-mt_uTzRcSiUQ-) ## Opens up - [Critical Exponents, Scaling and Universality](https://lightmysky.com/learn/science/critical-exponents-scaling-and-universality-mt_EaJOjyvjjj)