Unusual Electrical Transport Driven by the Competition between Antiferromagnetism and Ferromagnetism in Antiperovskite Mn₃Zn1-xCoxN.

Lihua Chu,Cong Wang,Lei Ding,Zhuohai Liu,Yanjiao Guo,Meicheng Li

doi:10.3390/ma11020286

Abstract

The magnetic, electrical transport and thermal expansion properties of Mn3Zn1−xCoxN (x = 0.2, 0.4, 0.5, 0.7, 0.9) have been systematically investigated. Co-doping in Mn3ZnN complicates the magnetic interactions, leading to a competition between antiferromagnetism and ferromagnetism. Abrupt resistivity jump phenomenon and negative thermal expansion behavior, both associated with the complex magnetic transition, are revealed in all studied cases. Furthermore, semiconductor-like transport behavior is found in sample x = 0.7, distinct from the metallic behavior in other samples. Below 50 K, resistivity minimum is observed in samples x = 0.4, 0.7, and 0.9, mainly caused by e-e scattering mechanism. We finally discussed the strong correlation among unusual electrical transport, negative thermal expansion and magnetic transition in Mn3Zn1−xCoxN, which allows us to conclude that the observed unusual electrical transport properties are attributed to the shift of the Fermi energy surface entailed by the abrupt lattice contraction.

Highlights

Mn3 XN (X: transition metals or semiconducting elements) and with a noncollinear magnetic ground state induced by the geometric frustration in the Mn6 N octahedron have been shown to exhibit fascinating physical properties, such as abnormal thermal expansion including negative thermal expansion (NTE) and zero thermal expansion etc. [1,2,3], near-zero temperature coefficient of resistivity (TCR) [4,5,6], magnetostriction [7], spin-glass (SG) behavior [8,9,10] and magnetocaloric effect [11,12]
To explain the unusual electrical transport behavior, we investigated the thermal expansion temperatures reveal that all samples crystallize into cubic cells with space group Pm-3m, and no behavior of Mn3 Zn1 − x Cox N series using variable temperature XRD
The effect of Co doping on the magnetic, thermal expansion and resistivity properties of antiperovskite Mn3 Zn1−x Cox N compounds was investigated

Summary

Introduction

As a strongly correlated electron system, antiperovskite compounds with a chemical formulaMn3 XN (X: transition metals or semiconducting elements) and with a noncollinear magnetic ground state induced by the geometric frustration in the Mn6 N octahedron have been shown to exhibit fascinating physical properties, such as abnormal thermal expansion including negative thermal expansion (NTE) and zero thermal expansion etc. [1,2,3], near-zero temperature coefficient of resistivity (TCR) [4,5,6], magnetostriction [7], spin-glass (SG) behavior [8,9,10] and magnetocaloric effect [11,12].It has been found that these interesting physical properties are sensitive to the number of the valence electrons of metal X located at the corners of antiperovskite unit cell, which contributes itinerant electrons at the Fermi level [13]. Any change in carrier concentration of Mn3 XN has a significant impact on its electronic structure, and may produce great diversity of its magnetic structures and related novel physical phenomena [14]. Among these antiperovskite compounds, Mn3 ZnN with the so-called noncollinear Γ5g antiferromagnetic (AFM) structure, has attracted considerable attention [15,16]. Recent reports have shown that the introduction of Co could effectively tune the physical properties in antiperovskites, such as the near zero TCR in Mn3−x Cox CuN [25] and the AFM-FM transition in Mn3 Ag1−x Cox N [26]. Since Co bears a similar electronic structure to that of Zn, introducing magnetic Co in Mn3 ZnN may provide new insight into the understanding of the origin of these novel physical properties

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Results

Conclusion