Experimental realisation of off-stoichiometric Fe-Mn-Si full Heusler alloy with hexagonal crystal structure by pulsed laser deposition

Publication date: 5 April 2018
Source:Materials & Design, Volume 143
Author(s): N.R. Checca, R.J. Caraballo-Vivas, A.A. Coelho, A. Rossi, N.M. Fortunato, F. Mohseni, J.N. Gonçalves, J.S. Amaral, D.L. Rocco, M.S. Reis
Full Heusler alloys are well known to either crystallize in a cubic structure (Cu2MnAl-type), or present tetragonal distortions. Both structure types present interesting properties, like room temperature magnetic memory shape effect and/or remarkable magnetocaloric effect, mainly ruled by strong magnetostructural coupling. Due to this interplay, our aim was to produce a new crystal phase for the Heusler alloys, different from those well-established cubic and tetragonal, responsible for those well-known physical properties. Thus, we have produced nanoparticles of full Heusler alloys using a pulsed laser deposition technique (from targets of Fe2MnSi) and obtained a core-shell pattern, presenting an amorphous shell and a crystalline core, with hexagonal symmetry. In accordance with these experimental findings, it was shown, by means of density functional calculation, the existence of a minimum of energy as a function of the hexagonal lattice parameters, with a true indication that the hexagonal phase is metastable. The magnetic properties differ considerably from those of bulk Fe2MnSi, including an increase of the Curie temperature from 220 K to 295 K, which is of potential interest for room-temperature applications. This work opens the door to research in a new family of materials, whose properties have only now begun to be explored.

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