Abstract: An apparatus for controlling and adjusting the magnetic state of a magnetic probe for detecting magnetic signals of a sample, it employs a negative feedback control unit to counter the change of magnetization of the magnetic probe. The local magnetic field of the sample influences the magnetization of the magnetic probe. Through the feedback coil inductively coupled to the magnetic probe, the variation of magnetization of the magnetic probe is compensated by the magnetization induced by the feedback coil. This apparatus is capable of reducing the magnetic interaction between the magnetic probe and sample. Meanwhile, a current bias unit is used for adjusting the magnetization of the magnetic probe to an arbitrary value. This capability allows a scanning probe microscope applying this invention to manipulate magnetic objects.

Abstract: A scanning probe microscope comprises a magnetic sensor and a sensor of electric tunneling current. The miscroscope integrates both the advantages of scanning SQUID microscope (SSM), and scanning tunneling microscope (STM), into a single instrument by applying a high-permeability metallic tip such as a permalloy tip, a pick-up coil and a transformer coupling the tip and the SQUID chip together. The local magnetic field of the test sample induces a substantial magnetization in the probing tip of high permeability. Through the pick-up coil inductively coupled to the tip, the magnetic signal of the induced moment is transferred to the SQUID chip via the transformer to achieve the best flux transferring condition. The metallic tip has the capability of sensing tunneling current and thus this instrument can also retain the capabilities of the STM, such as topography, current images and mappings of local density of state.