Hydrostatic pressure-tuned magnetostructural transition and magnetocaloric effect in Mn-Co-Ge-In compounds

F X Liang,F R Shen,Y Liu,J R Sun,K M Qiao,B G Shen,F X Hu,J Wang,J Li

doi:10.1063/1.5006688

Abstract

Polycrystalline MnCoGe0.99In0.01 with magnetostructural transition temperature (Tmstr) around 330 K has been prepared by arc-melting technique, and the pressure-tuned magnetostructural transition as well as the magnetocaloric effect (MCE) has been investigated. The experimental results indicate that a pressure (P) smaller than 0.53 GPa can shift Tmstr to lower temperature at a considerable rate of 119 K/GPa with the coupled nature of magnetostructural transition unchanged. However, as P reaches 0.53 GPa, the martensitic structural transition temperature (TM) further shifts to 254 K while the magnetic transition temperature of austenitic phase (TCA) occurs at around 282 K, denoting the decoupling of magnetostructural transition. Further increasing P to 0.87 GPa leads the further shift of TM to a lower temperature while the TCA keeps nearly unchanged. Therefore, the entropy change (ΔS) of the MnCoGe0.99In0.01 under different magnetic fields can be tailored by adjusting the hydrostatic pressure.

Highlights

MnCoGe-based materials with Ni2In-type hexagonal structure[1,2,3,4,5,6,7] show large magnetocaloric effect (MCE),[1] barocaloric effect (BCE)[2] and giant negative thermal expansion (NTE)[3] behavior.These multifunctional properties warrant people’s interest for this kind of materials due to the potential application in solid state refrigeration technique, as well as high-precision pressure-sensitive sensors and devices
It was found that the replacement of Mn by Al makes the martensitic transformation temperature decrease, as a result, a first-order magnetostructural transition occurs at 0 ≤ x ≤ 0.01 (For x = 0, the Mn loss during the melting is supposed to be responsible for the coupling of the structural and magnetic transitions.)
Sharply decreases for the case of P=0.87 GPa due to the notable reduction of saturated magnetization (figure 1(b) and its inset). These results suggest that an application of hydrostatic pressure smaller than 0.87 GPa is an effective way in tuning the magnetocaloric effect for present MnCoGe0.99In0.01 alloy

Summary

INTRODUCTION

MnCoGe-based materials with Ni2In-type hexagonal structure[1,2,3,4,5,6,7] show large magnetocaloric effect (MCE),[1] barocaloric effect (BCE)[2] and giant negative thermal expansion (NTE)[3] behavior. These multifunctional properties warrant people’s interest for this kind of materials due to the potential application in solid state refrigeration technique, as well as high-precision pressure-sensitive sensors and devices. As the pressure reaches 0.53 GPa, TM is further pushed to 254 K while T CA is still at a much higher temperature about 282 K, demonstrating the decoupling of magnetic and structural transition

EXPERIMENTAL DETAILS

RESULTS AND DISCUSSION

CONCLUSION