Joint motors are the core power source of highly dynamic humanoid robots, requiring designs with high torque density and low torque ripple. Due to the unique permanent magnet arrangement, Halbach array with a magnetic flux focusing effect is a promising candidate for use in joint motors of humanoid robots. Based on various Halbach array configurations (two-segment, three-segment, and four-segment) and magnetization angles, this paper investigates the difference of electromagnetic performance between traditional radial magnetization and Halbach array configurations in outer rotor permanent magnet synchronous motors (PMSMs), including air gap flux density, back EMF, cogging torque, electromagnetic torque, and motor losses. The results indicate that each Halbach array configuration has an optimal magnetization angle to achieve the maximum torque. Moreover, the three-segment Halbach array configuration shows an 11.4% improvement in electromagnetic torque and a 21.44% reduction in torque ripple compared to the traditional radial magnetization, significantly enhancing the motor's electromagnetic performance.