Abstract
Martensitic transformation (MT) and magnetic properties were investigated in a polycrystalline Ni-Mn-Ga freestanding and a sputter deposited on Al2O3 substrate films with excess Ni and Ga. Both films had a 2-μm thickness and MT above the room temperature. The MT region was wider in the freestanding film. The films demonstrated the isotropic in-plane behaviour of magnetic properties. A step-like behaviour was observed in the magnetization reversal process in the freestanding film because there were second-phase impurities. In the substrate-constrained film, only broadening in magnetization loops because of internal stresses was observed. The easy magnetization axis oriented normally to the film plane of the freestanding film but had a preferred orientation in the film plane of the substrate-constrained film. Both films exhibited a maze-like surface magnetic domain structure with the domain width of approximately 0.9 μm with different stripe structures, which confirms the presence of out-of-plane anisotropy. Based on these results, the effects of the substrate on the MT, structural and magnetic properties and the type of internal stresses were discussed.
Original language | English |
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Pages (from-to) | 1098-1104 |
Number of pages | 7 |
Journal | Journal of Alloys and Compounds |
Volume | 741 |
DOIs | |
Publication status | Published - 2018 Apr 15 |
Keywords
- Heusler alloys
- Magnetic and resistance measurements
- Magnetization
- Phase transitions
- Substrate-constrained and freestanding films
ASJC Scopus subject areas
- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys
- Materials Chemistry