Effect of Co, Ni, and Co-Ni doping on magnetic and electronic properties of MnBi by first-principles calculations

While Manganese Bismuth (MnBi) is a well-studied rare-earth free permanent magnetic material, its magnetic and electronic properties in the presence of dopants have not been discovered extensively. We studied the magnetic and electronic properties of MnBi doped with Co, Ni, and Co-Ni using the Generalized Gradient Approximation (GGA) method within Density Functional Theory (DFT). GGA+U method is used to get electronic correlation in 3d electrons in transition metal alloys. We considered both interstitial and substitutional sites in the MnBi lattice when adding Co, Ni, and Co-Ni. The addition of Co, Ni, and Co-Ni into interstitial sites has yielded a significant increase in the magnetization with dopant concentration. However substitutional doping into Mn site decreased its magnetization with dopant concentration. Our results show that individual Co and Ni doping prefers parallel spin configurations with Mn site while Co-Ni doping prefers both parallel and antiparallel configurations. We further calculated magnetic anisotropy energy (MAE) and magnetic anisotropy constant (K_u) of pure MnBi and doped-MnBi. Electronic properties were examined to describe exchange interactions between the dopants and the MnBi lattice.