Magnetooptical sensors using in-plane biased garnet films supporting domains

Rare-earth iron garnet films are currently used as magnetooptical indicator films for visualization of magnetic leakage fields in nondestructive testing. For gray scale imaging in-plane magnetized films are used yielding a high spatial resolution. On the other hand, garnet films supporting magnetic domains can be prepared having a very high sensitivity, while their resolution is limited by the size of the domains. This behavior can be improved considerably by applying a bias induction B∥ in the plane of the sensor film. Just above the collapse-induction B∥,coll the in-plane magnetized film offers a high spatial resolution with still high sensitivity. Experiments demonstrate a clear improvement of the quality of the magnetooptical imaging. The experimental results are in agreement with calculations.