Papers by Author: Gianluca Calestani

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Authors: Lara Righi, Franca Albertini, Antonio Paoluzi, Simone Fabbrici, Elena Villa, Gianluca Calestani, Stefano Besseghini
Abstract: Magnetic and structural properties in multifunctional FSMA (Ferromagnetic Shape Memory Alloys) belonging to Heusler family are frequently related to the occurrence of structural modulation in martensitic phases. The highest MFIS (Magnetic Field Induced Strain) effect has been observed in Ni-Mn-Ga alloys showing martensitic modulated structures. Depending on the composition, pressure and temperature conditions, this periodic structural distortion, consisting of shuffling of atomic layers along specific crystallographic directions, accompanies the martensitic transformation. Over the years, different modulated martensitic structures have been observed and classified depending upon the periodicity of corresponding superstructure (nM with n=3, 5, 6, 7, 12 etc). On the other hand, it has been demonstrated that in most cases such structural modulation is incommensurate and the crystal structure can be solved by applying superspace approach. The crystallographic representation of different modulated structures, obtained by structure refinement on powder diffraction data, suggests a unified description where every different “nM” periodicity can be straightforwardly represented. It will be presented an overview illustrating structural features of several displacive modulated martensitic lattices. For a specific Ni-Mn-Ga composition, the evolution of structural modulation upon temperature change will be illustrated.
Authors: Anna Tampieri, Gian Carlo Celotti, Gianluca Calestani, S. Lesca
Authors: Franca Albertini, L. Morellon, P.A. Algarabel, M.R. Ibarra, L. Pareti, Gianluca Calestani
Authors: Franca Albertini, Antonio Paoluzi, L. Pareti, L. Nasi, Giancarlo Salviati, Gianluca Calestani
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