History-dependent nucleation and growth of the martensitic phase in the magnetic shape memory alloy Ni 45 Co 5 Mn 38 Sn 12
Year: 2011
Type: article
Abstract: We study through the time evolution of magnetization the low-temperature ($T$) dynamics of the metastable coexisting phases created by traversing different paths in magnetic field $H$ and $T$ space in a shape memory alloy system, Ni${}_{45}$Co${}_{5}$Mn${}_{38}$Sn${}_{12}$. It is shown that these coexisting phases consisting of a fraction of kinetically arrested austenite phase and a remaining fraction of low-$T$ equilibrium martensitic phase undergo a slow relaxation to low magnetization (martensitic) state but with very different thermomagnetic history-dependent rates at the same $T$ and $H$. We discovered that, when the nucleation of the martensitic phase is initiated at much lower $T$ through the de-arrest of the glasslike arrested state contrasted with the respective first-order transformation (through supercooling at much higher $T$), the long-time relaxation rate scales with the nonequilibrium phase fraction but has a very weak dependence on $T$. This is explained on the basis of the H-T path dependent size of the critical radii of the nuclei and the subsequent growth of the equilibrium phase through the motion of the interface.
Source: Physical Review B
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2005504622