DPG Phi
Verhandlungen
Verhandlungen
DPG

Berlin 2008 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

MM: Fachverband Metall- und Materialphysik

MM 36: Phase Transitions II

MM 36.1: Talk

Thursday, February 28, 2008, 11:45–12:00, H 0107

First Principles Investigation of Twin Boundary Motion in Magnetic Shape Memory Heusler Alloys — •Markus Ernst Gruner and Peter Entel — Fachbereich Physik, Universität Duisburg-Essen, 47048 Duisburg, Germany

In the martensitic phase of the magnetic shape memory (MSM) Heusler alloy Ni2MnGa, strains of up to 10 % can be induced by external magnetic fields, making the material a technologically relevant candidate for magneto-mechanical actuators. The MSM effect in near stoichiometric Ni2MnGa is connected with a modulated pseudotetragonal martensitic phase with c/a<1. It is attributed to a high mobility of the twin-boundaries in connection with a large magneto-crystalline anisotropy allowing the reorientation of martensitic twins with the help of a magnetic field thereby changing the shape of the crystal. So far, the origin of the high mobility of twin-boundaries in this phase is unresolved and empirical potentials permitting the simulation on the relevant length and time scales do not exist. We therefore attempt to close this gap by large scale ab initio calculations in the framework of density functional theory allowing the investigation of simplified models of martensitic twin boundaries for the different martensitic structures of Ni2MnGa with the help of contemporary supercomputers. First results indicate that for the low-temperature, non-modulated martensitic L10 structure with c/a>1, the energy needed for shifting a twin boundary is too large to be overcome by magneto-crystalline anisotropy.

[1] M. E. Gruner, P. Entel, I. Opahle, M. Richter, J. Mater. Sci. (accepted for publication)

100% | Mobile Layout | Deutsche Version | Contact/Imprint/Privacy
DPG-Physik > DPG-Verhandlungen > 2008 > Berlin