Crystal structure and magnetic properties of MnBi–Bi nanocomposite

Isolated NiAs-type MnBi nanoparticles of 10 nm diameter, embedded in a Bi matrix, were fabricated by melt-spinning and then annealing at 528 K for 1 h. A large coercivity, over 16 kOe at 300 K, with a positive temperature coefficient is observed. In agreement with bulk results, ac susceptibility measurements show a spin reorientation around 90 K coincident with an abrupt decrease in the coercivity with decreasing temperature. The high coercivity at 300 K is attributed to a mixture of nucleation and pinning mechanisms for magnetic reversal.