A device with a magnetized needle that can spin freely is called a compass.

Here's how it works:

* Magnetized needle: The needle is made of a magnetic material, usually iron, and is permanently magnetized.

* Free to spin: The needle is mounted on a pivot point, allowing it to rotate freely.

* Earth's magnetic field: The Earth has its own magnetic field. The compass needle aligns itself with this field, pointing towards the Earth's magnetic north pole.

This ability to align with the Earth's magnetic field is what makes compasses useful for navigation.