MLZ User Meeting 2022

The half- to full-Heusler transition in Ni_{1+x}MnSb

8 Dec 2022, 13:40

25m

Marriott

Talk (20 min + 5 min discussion) Structure Research Structure Research

Speaker

Michael Leitner

Description

Structural voids are a defining feature of the half-Heusler structure. Using temperature-dependent neutron diffraction, the disordering of these vacancies is followed across the C1${}_b$-L2${}_1$ transition in samples of Ni${}_{1+x}$MnSb for various Ni excesses $x$, demonstrating the second-order nature of this transition. Structure solution on high-resolution room-temperature neutron diffraction as well as X-ray diffraction data yields a vacancy content in excess of $1-x$, the concentration of constitutional vacancies in the ideal model of site occupations. This is mirrored by the increased lattice constant during temperature-dependent diffraction on cooling, implying an annihilation of the initial vacancy excess at elevated temperatures. The reason for this very slow time-scale of vacancy concentration equilibration as compared to typical systems will be discussed, and consequences for the materials properties will be pointed out.

P. Neibecker et al., phys. status solidi B 259, 2100174 (2022)