Giant magneto-elastic coupling and tricritical metamagnetism in Mn-based Pnma compounds

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• Dr. Karl Sandeman, Imperial College London
• Friday 21 May 2010, 14:00-15:00
• Physics East 217.

If you have a question about this talk, please contact Elizabeth Blackburn.

Large magneto-elastic interactions are crucial to a range of new, technological materials in which multiple order parameters exist simultaneously and are coupled. These include ferromagnetic shape memory materials, multiferroics and magnetic refrigerant materials. Despite its relevance, atomically-resolved observations of large magneto-elastic coupling within a given crystal structure are very rare.

I will describe our recent high resolution neutron diffraction studies of CoMnSi, a metallic helical metamagnet in which the thermal evolution of the helimagnetic state is accompanied by a change in inter-atomic distances of up to 2%, the largest ever found in a metallic magnet [1]. Our observations lead us to a picture of competing exchange interactions at particular values of nearest-neighbour Mn-Mn separation. This subtle exchange balance is probably the key to metamagnetism in a wide range of Mn-based Pnma compounds and should enable the synthesis of new materials with tailored metamagnetic transitions [2].

[1] A. Barcza et al., cond-mat/1003.1206 [2] Z. Gercsi et al., cond-mat/1003.5193

This talk is part of the Condensed Matter Physics Seminars series.

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• Bham Talks
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• Condensed Matter Physics Seminars
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