Magnets and Phase Transitions

The Ising model

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Ising model: neighbouring spins prefer to align; temperature randomises them.
• Below $T_c \approx 2.27$ (2D), spins align spontaneously: a phase transition.
• Near critical points, very different systems behave identically (universality).

Steps

1. A toy magnet
2. Hot and cold
3. Make a magnet
4. Onsager’s number
5. Push with a field
6. Universality