Structure of long-period tetragonal lattice formed by solid-state alloying in Bi-Mn double-layer thin films
It has been a well known fact that BI and Mn are, by melting, immiscible with each other and only a ferromagnetic phase, MnBi, forms by a peritectic reaction at 446°C between solid Mn and the melt. However, the authors succeeded in mixing these two atomic elements by simultaneous vacuum deposition and found that a new metastable phase, Mn3Bi, appears as a crystallization product of the as-deposited amorphous films at 180°C, when their composition is in a range 85 to 65 at% Mn. They derived its atomic arrangement only by means of high resolution electron microscopy. In the present investigation, double layer thin films, consisting of Bi layer (300 Å) and of Mn layer (200°Å), were prepared by successive deposition and were heated at 265°C, just below the melting point of Bi (271°C), for 150 to 200 hr. By this heat treatment, solid-state alloying reaction takes place at the interface between the two layers and as many as four kinds of new alloy phases were found to appear.