Growth of MnBi Films on Mica

Films of Bi and Mn were evaporated successively onto freshly cleaved mica and subsequently annealed. By this method one gets homogeneous, oriented MnBi films with a large specific Faraday rotation (80 to 120 deg/μm at a wavelength of 632.8 nm). The specific Faraday rotation depends on the Bi to Mn ratio in a reproducible manner. The growth of oriented MnBi was observed by means of electrical, magneto-optical, and electron microscopical methods. The growth takes place in two main steps: During deposition, the Bi film grows epitaxially on mica, with (0001)Bi ∥ (0001)mica and 1000Bi ∥ 1000mica. During annealing, the Mn atoms diffuse into the lattice of the Bi film. The resulting MnBi lattice has the same orientation as the Bi lattice grown first. The reproducibly large specific Faraday rotation may thereby be explained.