Low temperature a/b nanotwins in Ni50Mn25+xGa25−x Heusler alloys

Low temperature a/b nanotwins in Ni50Mn25+xGa25−x Heusler alloys

Článek WoS

We have found low temperature a/b nanotwins having (110) twinning plane in a five-layered modulated martensite phase of Ni50Mn25+xGa25−x (at. %) Heusler alloys and identified the particular region in phase diagram where the nanotwinning occurs. Evolution of the structure with decreasing temperature was studied by X-ray diffraction using single crystals exhibiting magnetic shape memory effect. The merging of (400) and (040) lines upon cooling for 2.6 < x < 3.5 indicated a/b nanotwinning originating from the refinement of initially coarse a/b twins. Refinement of the twins with decreasing temperature was observed directly using scanning electron microscopy. The prerequisite for nanotwinning is an extremely low twin boundary energy, which we estimated using first-principles calculations to be 0.16 meV/Å2. As the nanotwinning distorts the relation between the crystal lattice and the X-ray diffraction pattern, it should be taken into consideration in structural studies of Ni-Mn-Ga Heusler alloys.

We have found low temperature a/b nanotwins having (110) twinning plane in a five-layered modulated martensite phase of Ni50Mn25+xGa25−x (at. %) Heusler alloys and identified the particular region in phase diagram where the nanotwinning occurs. Evolution of the structure with decreasing temperature was studied by X-ray diffraction using single crystals exhibiting magnetic shape memory effect. The merging of (400) and (040) lines upon cooling for 2.6 < x < 3.5 indicated a/b nanotwinning originating from the refinement of initially coarse a/b twins. Refinement of the twins with decreasing temperature was observed directly using scanning electron microscopy. The prerequisite for nanotwinning is an extremely low twin boundary energy, which we estimated using first-principles calculations to be 0.16 meV/Å2. As the nanotwinning distorts the relation between the crystal lattice and the X-ray diffraction pattern, it should be taken into consideration in structural studies of Ni-Mn-Ga Heusler alloys.

nanotwinning, magnetic shape memory alloy, Heusler alloys

nanotwinning, magnetic shape memory alloy, Heusler alloys

STRAKA, L.; VEŘTÁT, P.; DRAHOKOUPIL, J.; ZELENÝ, M.; KOPEČEK, J.; SOZINOV, A.; HECZKO, O.

2019

09.08.2018

Springer Nature

2045-2322

Scientific Reports

8

1

Spojené království Velké Británie a Severního Irska

11943

-

11

http://link.springer.com/article/10.1038/s41598-018-30388-8

http://hdl.handle.net/11012/179549

s41598-018-30388-8