Effect of co-existing crystal structures on magnetic properties of Ni_2Mn_(1+x)Sn_(1-x) magnetic shape memory alloy

TL;DR

This study investigates how co-existing crystal structures in Ni_2Mn_(1+x)Sn_(1-x) alloys influence their magnetic properties, revealing temperature-dependent structural changes and their impact on magnetic coupling and phenomena.

Contribution

It provides new insights into the relationship between multiple orthorhombic structures and magnetic behavior in Ni-Mn-Sn alloys, including spin glass and exchange bias effects.

Findings

Different orthorhombic structures have distinct antiferromagnetic coupling strengths.

Structural phase fractions change with temperature.

Explains origin of spin glass behavior and exchange bias effects.

Abstract

The temperature dependent crystal structure analysis in martensitic phase of Ni_2Mn_(1+x)Sn_(1-x) (x = 0.40 and 0.44) magnetic shape memory alloy is performed using X-ray diffraction. The martensitic phase consists of 4-Layered and 14-Layered orthorhombic structure. The phase fraction of 4-layered and 14-layered orthorhombic structure change with temperature. Interestingly, the magnetic property also changes with temperature and corresponds to structural change temperature. Thus, the exchange coupling constant between original Mn and substituted Mn is calculated, which shows that the 4-layered and 14-layered orthorhombic structures have different strength of antiferromagnetic coupling. The analysis explain the origin of spin glass behavior and unusual exchange bias effect in these systems under zero-field-cooling.