Investigation of the Mechanical, Electronic and Phonon Properties of X2ScAl (X = Ir, Os, and Pt) Heusler Compounds

In the present study, the second-order elastic constants and the electronic band structures of the X2ScAl (x = Ir, Os, and Pt) compounds crystallized in the L21 phase were calculated separately by using the ab-initio density functional theory. According to the results for the second-order elastic constants, these compounds met the Born mechanical stability criteria. Also, according to the Pugh criteria, they were found to have a ductile structure and to show anisotropic behavior. The microhardneses of the compounds were between 2 and 14 GPa, and the highest hardness was found in the Ir2ScAl (14.290 GPa) compound. In addition, the energy band structures of these compounds were calculated, and the crystals were found to have a metallic bond structure. All the computed data were compared with previously calculated results obtained with different methods. According to the findings obtained in the present study, in terms of its mechanical and electronic behaviors, Ir2ScAl was found to have better physical properties than Os2ScAl and Pt2ScAl. The phonon dispersion curves and their corresponding total and projected densities of states were investigated for the first time by using a linear-response approach in the context of density functional perturbation theory. The frequencies of the optical phonon modes of all compounds at the Γ point were 4.767, 7.504 and 9.271 THz for Ir2ScAl, 2.761, 7.985 and 9.184 THz for Os2ScAl and 2.012, 5.6952 and 8.118 THz for Pt2ScAl. The heat capacity Cv at constant volume versus temperature was calculated using a quasi-harmonic approach and the results are discussed. © 2020, The Korean Physical Society

Prediction of the Bain spin memory materials (BSMM) revealed by Kaneyoshi theory

In this work, we investigate the spin transformation from ferromagnetic austenite BCT lattice to antiferromagnetic martensite BCC lattice (j(i) = +J -> j(i) = -J or up arrow up arrow ->up arrow down arrow) in Bain transformation (or Bain strain) by using effective field theory which is developed by Kaneyoshi. We find that the spin orientation changes the magnetic properties in the Bain BCT -> BCC transformation. Therefore, we predict that material can memory their spin orientations in the austenite-martensite transformation similar to the shape memory effect in the shape memory materials. Since the austenite-martensite transformation mechanism is first modelled by Bain, we call this spin memory effect as 'Bain spin memory materials (BSMM)'

Transverse Field Effects of Al Concentration on Magnetic Properties of B2-FeAl Nanoparticle

Transverse field dependence of magnetic properties of the B2-FeAl nanoparticle (B2-FeAl-np) is investigated by using the effective field theory (or the Kaneyoshi theory) at H = 0 and H = 0.25. It is found that the magnetization and the Curie temperature of B2-FeAl-np decrease as the transverse field increases. A similar decrease in the magnetization and the Curie temperature of B2-FeAl is experimentally observed by Plazaola et al. with the increase (27.5%, 30%, 32.5% and 35%) of the Al content in B2-FeAl. These theoretical and experimental results revealed that the increase of the Al content in B2-FeAl-np causes an increase in the transverse field of B2-FeAl-np. Thus, the magnetization and the Curie temperature of B2-FeAl-np decrease. However, the ferromagnetic and antiferromagnetic spin splitting of paramagnetic Fe and Al atoms is obtained by a non-zero external magnetic field (H = 0.25) at T > T-C