Discussion on several principal problems aroused from measuring high performance permanent magnetic materials

The standard method for measuring magnetic properties of permanent magnets is the closed circuit method using an iron-cored electromagnet. With the advances of modern high quality permanent magnetic materials, it has become more and more important to measure their magnetic properties accurately both at room and elevated temperatures. Many problems have arisen when using this traditional DC hysteresigraph to test these new materials, such as those based on rare earth intermetallic compounds, bonded magnetic materials and nanocrystalline exchange-coupled magnets. The physical knowledge on these principal problems including magnetic properties of material, magnetic properties of product, specimen, uniform magnetization, saturation magnetization, the influence of the saturation of the poles, and the influence of Hall probe, etc., is important in the research and development of new materials and also nondestructive evaluation (NDE). These problems are discussed in this paper qualitatively and the current statuses to solve these problems are also presented.