Magnetocaloric Effect, Magnetoresistance of Sc0.28Ti0.72Fe2, and Phase Diagrams of Sc0.28Ti0.72Fe2−xTx Alloys with T = Mn or Co

Liting Sun,Francois Guillou,Ojiyed Tegus,Hargen Yibole

doi:10.3390/cryst10050410

Abstract

(Sc,Ti)Fe2 Laves phases present a relatively unique case of first-order ferro-ferromagnetic transition originating from an instability of the Fe moment. In addition to large magnetoelastic effects making them potential negative thermal expansion materials, here, we show that Sc0.28Ti0.72Fe2 and related alloys also present sizable magnetocaloric and magnetoresistance effects. Both effects are found substantially larger at the ferro-ferromagnetic transition (Tt1) than near the Curie temperature TC, yet they remain limited in comparison to other classes of giant magnetocaloric materials. We suggest a strategy to improve these properties by bringing the transition at Tt1 close to TC, and test its possible realization by Co or Mn for Fe substitutions. The structural and magnetic phase diagrams of Sc0.28Ti0.72Fe2−xTx alloys with T = Mn or Co are explored. Substitutions for Fe by adjacent Mn or Co elements give rise to a breakdown of the long-range ferromagnetic order, as well as a swift disappearance of finite moment magnetism.

Highlights

AB2, form a large materials family exhibiting a vast array of intriguing properties, including those related to magnetism [1,2]
We explore the influence of Mn or Co for Fe substitutions in Sc0.28 Ti0.72 Fe2−x Tx and establish structural and magnetic phase diagrams of these quaternary alloys
The magnetocaloric and magnetoresistance effects of Sc0.28 Ti0.72 Fe2 Laves phase were investigated. Both effects were found to be substantially larger at the first-order ferro-ferromagnetic transition (Tt1 )

Summary

Introduction

AB2 , form a large materials family exhibiting a vast array of intriguing properties, including those related to magnetism [1,2]. Around 50–120 K with a change in amplitude of the magnetic moment [13,14,15,16] This FM–FM transition is associated with a large magnetoelastic effect and corresponds to an increase upon cooling of the Fe magnetic moments from ~0.9 μB /Fe to ~1.3 μB /Fe, breaking down a local moment description. Local probes such as Mössbauer spectroscopy have shown that the Fe moment in the 2a position is highly dependent on the composition [14], and neutron diffraction experiments revealed that an instability of the Fe moment in the 2a position occurs as a function of temperature [17].

Methods

Results

Conclusion