Phonon softening in Ni-Mn-Ga alloys
نویسندگان
چکیده
The TA2 phonon dispersion curves of Ni-Mn-Ga alloys with different compositions which transform to different martensitic structures have been measured over a broad temperature range covering both paramagnetic and ferromagnetic phases. The branches show an anomaly (dip) at a wave number that depends on the particular martensitic structure, and there is softening of these anomalous phonons with decreasing temperature. This softening is enhanced below the Curie point, as a consequence of spin-phonon coupling. This effect is stronger for systems with higher electronic concentration.
منابع مشابه
A critical discussion of calculated modulated structures , Fermi surface nesting and phonon softening in magnetic shape memory alloys Ni 2 Mn ( Ga , Ge , Al ) and Co 2 Mn ( Ga , Ge )
A series of first principles calculations have been carried out in order to discuss electronic structure, phonon dynamics, structural instabilities and the nature of martensitic transformations of the Heusler alloys Ni2Mn(Ga, Ge, Al) and Co2Mn(Ga, Ge). The calculations show that besides electronic pecularities like Fermi–surface nesting, hybridizing optical and acoustic phonon modes are importa...
متن کاملElectronic structure and lattice dynamics of the magnetic shape-memory alloy Co2NiGa
In addition to the prototypical Ni-Mn-based Heusler alloys, the Co-Ni-Ga systems have recently been suggested as another prospective materials class for magnetic shape-memory applications. We provide a characterization of the dynamical properties of this material and their relation to the electronic structure within a combined experimental and theoretical approach. This relies on inelastic neut...
متن کاملProperty Investigations with an Automat Correlation Routine and Applications for a Set of Alloys
The present paper is focused on modeling of statistical data processing with applications in field of material science and engineering. A new method of data processing is presented and applied on a set of 10 Ni–Mn–Ga ferromagnetic ordered shape memory alloys that are known to exhibit phonon softening and soft mode condensation into a premartensitic phase prior to the martensitic transformation ...
متن کاملFerromagnetic shape memory alloys: Alternatives to Ni–Mn–Ga
This paper intends to review the state-of-the-art in the field of ferromagnetic shape memory alloys different than Ni–Mn–Ga, developed in the ast years. It starts with the effects of additions of different fourth elements to Ni–Mn–Ga and continues with the review of other Heusler (or B2) i-based and Co-based alloy systems, like Ni–Mn–X, Ni–Fe–Ga, Co–Ni–Al and Co–Ni–Ga alloys. Finally, ferromagn...
متن کاملLattice dynamics and phonon softening in Ni-Mn-Al Heusler alloys
Inelastic and elastic neutron scattering have been used to study a single crystal of the Ni54Mn23Al23 Heusler alloy over a broad temperature range. The paper reports the experimental determination of the low-lying phonon dispersion curves for this alloy system. We find that the frequencies of the TA2 modes are relatively low. This branch exhibits an anomaly (dip) at a wave numberξ0=1∕3≈0.33, wh...
متن کامل