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Excess vacancies and structural ordering

Increasing the achievable state of order in Ni-based Heusler alloys via quenched-in vacancies

This is our short work reporting a finding that in hindsight is perhaps obvious, but nevertheless of substantial relevance in application: If it is possible to quench an excess vacancy concentration in a given system, then it can become possible to reach ordering states that are only stable at low temperature, where near-equilibrium kinetics would otherwise make the ordering process prohibitively slow. In essence, the activation energy of atomic diffusion (and thus ordering) consists only of the vacancy migration energy in this case — as long as there are excess vacancies, it is not necessary to form them. Our experimental findings were now that in a specific Ni-based Heusler alloy (Ni2MnAl, but likely also in related systems) both the achievable vacancy excess concentration, as well as their lifetimes are large enough for this to significantly affect the material's properties after annealing.

It is published in Applied Physics Letters, volume 105, 261904. After a period of 12 months, I am now allowed to make the version of record available, note that the copyright is held by AIP Publishing.
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