Magnetic properties of MnBi particles

Platelet-shaped MnBi particles with diameter smaller than 0.5 μm were prepared by grinding sintered MnBi in a ball mill. The MnBi particles were dispersed and oriented in a polymer binder. The oriented MnBi particles were demagnetized in cooling to 85 °K, at which the coercivity was about 300 Oe. The applied magnetic-field dependence of coercivity was measured at 300 °K on the demagnetized MnBi particles. The coercivity remarkably increased with increasing strength of magnetic field, and in a magnetic field strength of 16 kOe, the maximum coercivity of 16 kOe was attained. It is suggested that ’’nuclei’’ from which magnetization reversal occurs exist in particles in the demagnetized state, and disappear by applying a strong magnetic field.