Author : Jing Bai
Publisher :
ISBN 13 :
Total Pages : 22 pages
Book Rating : 4.:/5 (8 download)
Book Synopsis Study on Structural, Electronic and Magnetic Properties of Ni-Mn-Ga and Ni-Mn-In Ferromagnetic Shape Memory Alloy Systems by : Jing Bai
Download or read book Study on Structural, Electronic and Magnetic Properties of Ni-Mn-Ga and Ni-Mn-In Ferromagnetic Shape Memory Alloy Systems written by Jing Bai and published by . This book was released on 2011 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ferromagnetic shape memory alloys (FSMAs) are novel smart materials which exhibit magnetic field induced strains of up to 10 %. As such they have potential for many technological applications. Also, the strong magnetostructural couplings of the FMSM effect make the phenomenon very interesting from a scientific point of view. In the present work, a series of first-principles calculations have been performed within the framework of the Density Functional Theory (DFT) using the Vienna Ab initio Software Package (VASP). In the stoichiometric Ni2XY (X=Mn, Fe, Co; Y=Ga, In) alloys, lattice parameters, atomic separations, total and partial magnetic moments decrease gradually with the increase in the X atomic number; whereas the bulk modulus displays an opposite tendency. The formation energy indicates a destabilization tendency if Mn is substituted by Fe or Co, or Ga is replaced by In. The strong bond between neighboring Ni atoms in Ni2MnGa is replaced by the bond between Ni and X atoms in other alloys. For the off-stoichiometric Ni2XY (X=Mn, Fe, Co; Y=Ga, In), the formation energies of several kinds of defects (atomic exchange, antisite, vacancy) were calculated. For most cases of the site occupation, the excess atoms of the rich component directly occupy the site(s) of the deficient one(s), except for Y-rich Ni-deficient composition. In the latter case, the defect pair (YX + XNi) is energetically more favorable. The value of Ni magnetic moment sensitively depends on the distance between Ni and X atoms. The effects of Co addition on the properties of Ni8-xMn4Ga4Cox (x=0-2) FSMAs were systematically investigated. The added Co atoms preferentially occupy the Ni sites. The calculated formation energies indicate a structural instability with the increase in the Co content for both paramagnetic (PA) and ferromagnetic austenite (FA). The total energy difference between PA and FA increases, which results in the rise of Tc when Ni is replaced by Co. Insights into fundamental aspects such as crystallography, phase stability, and electronic structure in Ni-X-Y (X=Mn, Fe, Co; Y=Ga, In) FSMAs are of great significance to improve the functional performances and to design new promising FSMAs.
