Parts | Days | Selection | Search | Updates | Downloads | Help

MM: Fachverband Metall- und Materialphysik

MM 38: Topical Session Diffussionless Transformations I

MM 38.5: Talk

Thursday, March 17, 2011, 15:15–15:30, IFW D

Probing the electronic origin of a martensitic transformation in frozen intermediate stages. — •X. Kozina¹, S. Weiss², L. Schultz², S. Fähler², G. Stryganyuk¹, S. Ouardi¹, G. H. Fecher¹, C. Felser¹, S. Ueda³, and K. Kobayashi³ — ¹Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg - University, Mainz, Germany — ²IFW Dresden, Germany — ³National Institute for Materials Science, SPring-8, Hyogo, Japan

An energetically unfavourable high density of states close to Fermi level had been suggested as driving force for martensitic transformation in metals. Here we present a direct experimental proof for the Fe₇₀Pd₃₀ magnetic shape memory alloy. By coherent epitaxial film growth we stabilize intermediate stages along the Bain transformation path, connecting bcc and fcc structure. This allows a detailed analysis at a constant temperature of 300 K, in vicinity of the martensitic transformation temperature. For probing the electronic structure of these 50 nm-thick films hard X-ray photoelectron spectroscopy (HAXPES) at BL15XU at SPring-8 was used. High probing depth of this method makes it a unique, non-destructive tool for studying electronic properties of thin films without taking into account the quality of the surface. Further, at high excitation energies one reaches nearly equal spectral weight for all states. Our measurements reveal that the density of states at 2 eV below the Fermi energy is reduced by 4,6% when the structure changes from the fcc austenite towards the bcc martensite. This confirms the proposed band Jahn Teller effect. This work is supported by DFG through SPP 1239 and DfG-JST (FE633/6-1).