Abstract: A tension test is used to investigate the mechanical properties of three magnetic materials for the magnetic torque, namely, ferronickel, ferro-cobalt, and ferro. aluminium. Because the three materials have different plasticities。their fractures should appear in different positions in the specimens, which are the weak positions, while for brittle materials, damages appear at the clip positions of the stress concentration. A finite element analysis shows that the length of the weak part and me stress concentration at the clip part determine the fracture position in the tension test. Thus, an improvement of the design is suggested with another round of simulation analysis. It is shown that for the improved specimens of three materials under the same conditions. the fractures all occur at their weak part. and are less affected by the stress concentration. The reasonable mechanical properties of these three materials can thus be obtained.