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Collective Modes and Structural Modulation in Ni-Mn-Ga(Co) Martensite Thin Films Probed by Femtosecond Spectroscopy
M Schubert1, H Schaefer1,2, J Mayer1
1Department of Physics, University of Konstanz, 78457 Konstanz, Germany.
Physical Review Letters
|August 29, 2015
Summary
The martensitic phase transition in Ni-Mn-Ga magnetic shape memory alloys is driven by a charge-density wave. This complex phenomenon is influenced by magnetic ordering and electron-lattice coupling.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Solid State Chemistry
Background:
- The origin of the martensitic transition in Ni-Mn-Ga magnetic shape memory alloys is a subject of ongoing debate.
- Existing theories propose either an electronically driven transition or an adaptive martensite model explaining lattice modulations.
Purpose of the Study:
- To investigate the underlying mechanism of the martensitic transition in Ni-Mn-Ga.
- To elucidate the interplay between electronic, magnetic, and lattice properties during the phase transition.
Main Methods:
- Femtosecond spectroscopy was employed to study temperature and doping effects on collective modes.
- Scanning tunneling microscopy was utilized to observe static lattice modulations.
Main Results:
- The study reveals that the martensitic phase is characterized by a complex charge-density wave.
- This charge-density wave is modulated by magnetic ordering.
- Strong electron-lattice coupling plays a crucial role in the transition.
Conclusions:
- The martensitic phase transition in Ni-Mn-Ga is best described as a charge-density wave phenomenon.
- Magnetic ordering and electron-lattice coupling are key factors governing this transition.
