Contents I. Introduction
Soft magnetic materials have the advantages of high permeability, high saturation magnetic flux density, small coercivity, which not only meet the development requirements of traditional industry, but also play an increasingly important role in the fields of communication, power supply, computer and various electronic products[1–3]. With the rapid improvement of weak magnetic technology, new soft magnetic materials with different functions have been prepared. The magnetic properties of soft magnetic materials have increasingly greater impacts on the performance of instruments and equipment. Therefore, the measurement and screening of magnetic properties of soft magnetic materials are becoming more and more important. In order to characterize the magnetization of these soft magnetic materials and monitor their behavior, a sensitive detection method is required. Several techniques have been developed for detecting weak magnetic fields, for example, superconducting quantum interference devices (SQUIDs), alternating gradient magnetometers (AGM), vibrating sample magnetometer (VSM) et al [4–7]. Each method has both advantages and disadvantages. For example, SQUIDs offer ultrahigh sensitivity and have been used extensively to detect weak magnetic signals, but they require cryogenics. Vibrating sample magnetometer and alternating gradient magnetometer have relatively low sensitivity.
