Dimensionality tuning of the electronic structure in Fe3Ga4 magnetic materials.

K O Moura,E Granado,P G Pagliuso,L A S De Oliveira,C B R Jesus,K R Pirota,M E Saleta,F Béron,P F S Rosa

doi:10.1038/srep28364

K O Moura, E Granado + Show 7 more

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https://doi.org/10.1038/srep28364

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Abstract

This work reports on the dimensionality effects on the magnetic behavior of Fe3Ga4 compounds by means of magnetic susceptibility, electrical resistivity, and specific heat measurements. Our results show that reducing the Fe3Ga4 dimensionality, via nanowire shape, intriguingly modifies its electronic structure. In particular, the bulk system exhibits two transitions, a ferromagnetic (FM) transition temperature at T1 = 50 K and an antiferromagnetic (AFM) one at T2 = 390 K. On the other hand, nanowires shift these transition temperatures, towards higher and lower temperature for T1 and T2, respectively. Moreover, the dimensionality reduction seems to also modify the microscopic nature of the T1 transition. Instead of a FM to AFM transition, as observed in the 3D system, a transition from FM to ferrimagnetic (FERRI) or to coexistence of FM and AFM phases is found for the nanowires. Our results allowed us to propose the magnetic field-temperature phase diagram for Fe3Ga4 in both bulk and nanostructured forms. The interesting microscopic tuning of the magnetic interactions induced by dimensionality in Fe3Ga4 opens a new route to optimize the use of such materials in nanostructured devices.

Highlights

Antiferromagnetism (AFM) takes place before vanishing at a Néel temperature T2 = 390 K13
Its energy dispersive X-ray spectrometry (EDS) mapping for Fe Kα and Ga Lα energies, shown respectively in Fig. 1(c–d), clearly states that both Fe and Ga elements are present in the nanowires
The quantitative chemical composition given by EDS was not used since the analyzed surface was not polished and that Fe has a weak detection power compared to Ga, due to its low atomic number

Summary

Introduction

Antiferromagnetism (AFM) takes place before vanishing at a Néel temperature T2 = 390 K13 This behavior has been explained by Moriya and Usami’s theory, which predicts coexistence of FM and AFM states in itinerant electron systems[13,14]. To investigate these peculiar magnetic and structural behaviors, several chemical substitution studies have been performed on both Fe and Ga sublattices[15,16,17,18]. We report the dimensionality effects on the Fe3Ga4 magnetic field-temperature phase diagram (H–T), which was constructed for both bulk and nanowire systems using magnetization, specific heat and electrical resistivity measurements. We strongly believe that the possibility of growing intermetallic compounds in nanowire form will open an interesting branch in the understanding of fundamental properties, as well as permitting to control the nanowire characteristics for desired applications

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