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
Abstract:
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.