Martensitic transformation in polycrystalline substrate-constrained and freestanding Ni-Mn-Ga films with Ni and Ga excess

S. Shevyrtalov, Hiroyuki Miki, Makoto Ohtsuka, A. Grunin, I. Lyatun, A. Mashirov, M. Seredina, V. Khovaylo, V. Rodionova

Research output: Contribution to journalArticle

3 Citations (Scopus)

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 languageEnglish
Pages (from-to)1098-1104
Number of pages7
JournalJournal of Alloys and Compounds
Volume741
DOIs
Publication statusPublished - 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

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