Neutron diffraction evidence for kinetic arrest of the first-order austenite to martensite transition in Ni37Co11Mn42.5Sn9.5

TL;DR

This study uses neutron diffraction under magnetic fields to demonstrate the kinetic arrest of the austenite to martensite transition in Ni37Co11Mn42.5Sn9.5, revealing a glass-like arrested state and mapping the phase diagram.

Contribution

It provides direct structural evidence for kinetic arrest and phase coexistence in a magnetic shape memory alloy using neutron diffraction and the CHUF protocol.

Findings

Kinetic arrest of phase transition confirmed by neutron diffraction.

Formation of a glass-like arrested state (GLAS) observed.

The phase diagram shows TK(H) increases with magnetic field H.

Abstract

Neutron diffraction measurements, performed in presence of an external magnetic field, have been used to show structural evidence for the kinetic arrest of the first-order phase transition from the high temperature austenite phase to the low temperature martensite phase in the magnetic shape memory alloy Ni37Co11Mn42.5Sn9.5 and the formation of a glass-like arrested state (GLAS). The CHUF (cooling and heating under unequal fields) protocol has been used to establish phase coexistence of metastable and equilibrium states of GLAS in the neutron diffraction patterns. We also explore the field-temperature (H,T) phase diagram for this composition which depicts the kinetic arrest line TK(H). TK is seen to increase as H increases.