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Why is Earth’s geomagnetic field not produced by a giant bar magnet inside the planet?

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geomagnetic field The magnetic field of a bar magnet has a simple configuration known as a dipole field. Close to Earth's surface this field is a reasonable approximation of the actual field.

Earth’s geomagnetic field is not produced by a giant bar magnet inside the planet because the interior of Earth is far too hot to support permanent magnetism.

Materials that exhibit ferromagnetism—the property that allows a bar magnet to function—lose this ability when heated above a specific temperature known as the Curie point. For common magnetic materials like iron, this temperature is reached only about 10 to 40 kilometres (6 to 25 miles) beneath Earth’s surface. Given that temperatures in Earth’s core are estimated to be between 4,000 and 7,000 K, any permanent magnetic material would be well above its Curie point and thus incapable of maintaining a magnetic field.123

Instead, scientists have concluded that the geomagnetic field is generated by a geomagnetic dynamo located within Earth’s liquid outer core. In this process, fluid motion of electrically conducting molten iron creates electric currents, which in turn produce and sustain the magnetic field. This self-sustaining mechanism is the only model currently considered capable of explaining the origin and maintenance of the planet's magnetic field.145