Basic Properties of Magnetic Shape-Memory Materials from First-Principles Calculations
In: Metallurgical and materials transactions A: Physical Metallurgy and Materials Science, Jg. 43 (2012) ; Nr. 8, S. 2891-2900
ISSN: 1543-1940, 1073-5623
Zeitschriftenaufsatz / Fach: Physik
Fakultät für Physik » Theoretische Physik
The mutual influence of phase transformations, magnetism, and electronic properties of magnetic-shape memory Heusler materials is a basic issue of electronic structure calculations based on density functional theory. In this article, we show that these calculations can be pursued to finite temperatures, which allows to derive on a first-principles basis the temperature versus composition phase diagram of the pseudo-binary Ni-Mn-(Ga, In, Sn, Sb) system. The free energy calculations show that the phonon contribution stabilizes the body-centered-cubic (bcc)-like austenite structure at elevated temperatures, whereas magnetism favors the lowtemperature martensite phase with body-centered-tetragonal (bct) or rather face-centeredtetragonal (fct) structure. The calculations also allow to make predictions of magnetostructural and magnetic field induced properties of other (new) magnetic Heusler alloys not based on NiMn such as Co-Ni-(Ga-Zn) and Fe-Co-Ni-(Ga-Zn) intermetallic compounds.