Kerr magnetometer

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Sketch Kerr magnetometer

A Kerr magnetometer is a type of magnetometer that uses the magneto-optical Kerr effect to measure .


The physicist John Kerr discovered that polarized light that hits a magnetized surface experiences a rotation of the plane of polarization . The reflected light beam also receives an oscillation component (rotation) in another plane. For example, the presence of the information "1" on a hard disk (magnetization of the storage location) causes such a rotation of the polarization plane, with the state "0" this rotation is missing. The Kerr rotation is only about 1 to 3 degrees . It can be detected with a Kerr magnetometer. When manufacturing hard disks, a Kerr magnetometer can be used to non-destructively test every point on the disk for its magnetic properties. This is a major application of the Kerr magnetometer.

Kerr magnetometer

For the detection of magnetization components lying in the layer plane, the sample to be examined is illuminated obliquely with polarized light (perpendicular to the plane of incidence) of a laser . The sample is located between two pole pieces of a field magnet. The magnetization causes a change in the polarization of light in the reflected beam. The light is put into an elliptical polarization state (Kerrelliptization) and additionally rotated by an angle (Kerr rotation). The Kerr angle can be determined from the signal amplitude of the investigated magnetic sample.

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