Evidence of bcc Mn epitaxial growth in Mn/MxV1-x(001) (M = Fe, Nb) superlattices

This study is dedicated to the growth of bcc Mn by molecular beam epitaxy, in order to look at the magnetic properties of bcc Mn near room temperature . For this purpose, Mn is deposited on bcc MxV1-x(001) alloy lattices (M = Fe or Nb) for which the lattice spacing is tunable by varying the concentra tion x. We first show that the parameter of the MxV1-x alloy's buffer layer s can be adjusted from 2.95 Angstrom to 3.3 Angstrom depending on x and M. Three different structures in Mn films grown on these buffer layers are obs erved depending on the in-plane spacing of the initial MxV1-x lattice. Thic k Mn films are always found to grow epitaxially in the Mn alpha structure. For moderate thicknesses larger than 4 atomic planes, Mn grows in an uniden tified structure. Finally, up to four deposited atomic planes, Mn is found to grow in a tetragonal structure close to a bcc one on Fe(001), FexV1-x(00 1) and NbxV1-x(001) for x less than or equal to 25%. This tetragonal struct ure is shown to be a distorsion of a nln bcc structure with a = 2.92 Angstr om. Except for ultra-thin Mn films deposited on Fe(001), no macroscopic mag netization is detected in our strained bcc Mn samples. These results are co mpared to theoretical predictions.