A new method of sensing bubble domain with magnetoresistive element

This paper describes a very sensitive detector for bubble domains using Permalloy magnetoresistive effect. In the conventional operation method of planar magnetoresistive elements they are arranged close to the circumference of a bubble domain, where the magnetic field runs parallel to the plane of elements. But even if the magnetic field is applied to the direction of the angle φ against the film plane, the value of magnetoresistance change ratio ΔR/R is, except near φ= π/2, similar to the one magnetized to the direction of the film plane, namely, φ = 0. This experiment is explained from the fact that the specimen is magnetized by the horizontal component of the applied field. Considering the magnetic field out of a bubble domain, this result refers that the detector is arranged not only at the circumference of domain but also above the surface and the outside of it. Then the detector of type is designed; its length is a, and its width and gap are a/6, where a is a bubble diameter. The sensing voltage of 15 mV can be obtained from a bubble domain of TmFeO3at driving current 7 mA, which is four or five times those of detection voltage published in the past.