Magnetic ordering of the martensite phase in Ni-Co-Mn-Sn-based ferromagnetic shape memory alloys

Sudip Kumar Sarkar; Sarita Ahlawat; S D Kaushik; P D Babu; Debasis Sen; Dirk Honecker; Aniruddha Biswas

doi:10.1088/1361-648X/ab5876

Magnetic ordering of the martensite phase in Ni-Co-Mn-Sn-based ferromagnetic shape memory alloys

J Phys Condens Matter. 2020 Mar 13;32(11):115801. doi: 10.1088/1361-648X/ab5876. Epub 2019 Nov 18.

Authors

Sudip Kumar Sarkar¹, Sarita Ahlawat, S D Kaushik, P D Babu, Debasis Sen, Dirk Honecker, Aniruddha Biswas

Affiliation

¹ Glass and Advanced Materials Division, Bhabha Atomic Research Centre, Mumbai 400085, India.

PMID: 31739303
DOI: 10.1088/1361-648X/ab5876

Abstract

The magnetic state of low temperature martensite phase in Co-substituted Ni-Mn-Sn-based ferromagnetic shape memory alloys (FSMAs) has been investigated, in view of numerous conflicting reports of occurrences of spin glass (SG), superparamagnetism (SPM) or long range anti-ferromagnetic (AF) ordering. Combination of DC magnetization, AC susceptibility and small angle neutron scattering (SANS) studies provide clear evidence for AF order in the martensitic phase of Ni₄₅Co₅Mn₃₈Sn₁₂ alloy and rule out SPM and SG orders. Identical studies on another alloy of close composition, Ni₄₄Co₆Mn₄₀Sn₁₀, point to the presence of SG order in the martensitic phase and the absence of SPM behavior, contrary to earlier reports. SANS results do show the presence of nanometre-sized clusters but they are found to grow in size from 3 nm at 30 K to 11 nm at 300 K, and do not correlate with magnetism in these alloys.