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Atomic and magnetic order in the shape memory alloy Mn2NiGa
P J Brown1, T Kanomata, K Neumann
1Department of Physics, Loughborough University, UK.
Summary
Magnetization and neutron diffraction reveal Mn(2)NiGa is a ferromagnetic shape memory alloy with a high Curie temperature. It exhibits a structural phase transformation and a unique martensitic phase with distinct magnetic properties.
Area of Science:
- Materials Science
- Solid State Physics
- Magnetism
Background:
- Magnetic shape memory alloys (MSMAs) are technologically important materials exhibiting unique magnetocaloric and mechanical properties.
- Understanding the interplay between structural and magnetic properties is crucial for MSMA applications.
Purpose of the Study:
- To investigate the magnetic and structural properties of the Mn(2)NiGa magnetic shape memory alloy.
- To characterize the phase transitions and magnetic ordering in Mn(2)NiGa.
Main Methods:
- Magnetization measurements were performed to determine magnetic properties and Curie temperature.
- High-resolution neutron powder diffraction was used to analyze crystal structure and phase transformations.
- Analysis of magnetic moments and structural changes at different temperatures.
Main Results:
- Mn(2)NiGa is ferromagnetic with a Curie temperature exceeding 500 K.
- A broad structural phase transformation occurs around 270 K, transitioning from a cubic parent phase to a tetragonal martensite.
- The magnetic moment is primarily located on Mn sites, increasing from 1.35 μ(B)/Mn at 500 K to approximately 2.3 μ(B)/Mn at 5 K.
- Evidence of a weak incommensurate antiferromagnetic phase was observed at 5 K.
Conclusions:
- Mn(2)NiGa exhibits complex magnetic and structural behavior characteristic of magnetic shape memory alloys.
- The material's properties are strongly dependent on temperature, with distinct magnetic ordering in the martensitic phase.
- Further investigation into the incommensurate antiferromagnetic phase is warranted.
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