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The present investigation was undertaken to investigate the effect of quenching rate on the microstructure of Ni 50 Mn 50 À x Sn x ribbon alloys and its influence on the martensitic starting phase-transition temperature M S . The study was performed on melt-spun ribbons of a ferromagnetic shape memory alloy (FSMA) of composition Ni 50 Mn 37 Sn 13 produced by varying the speed of the rotating copper wheel between 15 and 50 m s À1 . The resulting samples have a chemical composition close to the nominal one and at room temperature crystallize in a cubic single-phase austenite with the highly ordered L2 1 -type crystal structure without a significant variation in the cell parameter. The average grain size varies between 1.4 and 7.3 mm, while M S increased from 212 to 258 K. Our results suggest that in these materials the average grain size of the parent austenite phase limits the size of the martensite variants, giving rise to its stabilization, while a multivariant transformation mode is maintained.

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We report on the experimental and theoretical analysis of parametrical optomechanical oscillations in hollow spherical phoxonic whispering gallery mode resonators due to radiation pressure. The optically excited acoustic eigenmodes of the phoxonic cavity oscillate regeneratively leading to parametric oscillation instabilities.

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