Combined Bottom-Up and Top-Down Approach for Highly Ordered One-Dimensional Composite Nanostructures for Spin Insulatronics.

Gopal Datt,Ganesh Kotnana,Tapati Sarkar,Davide Peddis,Ramu Maddu,Gianni Barucca,Deep Chandra Joshi,M Venkata Kamalakar,Örjan Vallin

doi:10.1021/acsami.1c09582

Abstract

Engineering magnetic proximity effects-based devices requires developing efficient magnetic insulators. In particular, insulators, where magnetic phases show dramatic changes in texture on the nanometric level, could allow us to tune the proximity-induced exchange splitting at such distances. In this paper, we report the fabrication and characterization of highly ordered two-dimensional arrays of LaFeO3 (LFO)–CoFe2O4 (CFO) biphasic magnetic nanowires, grown on silicon substrates using a unique combination of bottom-up and top-down synthesis approaches. The regularity of the patterns was confirmed using atomic force microscopy and scanning electron microscopy techniques, whereas magnetic force microscopy images established the magnetic homogeneity of the patterned nanowires and absence of any magnetic debris between the wires. Transmission electron microscopy shows a close spatial correlation between the LFO and CFO phases, indicating strong grain-to-grain interfacial coupling, intrinsically different from the usual core–shell structures. Magnetic hysteresis loops reveal the ferrimagnetic nature of the composites up to room temperature and the presence of a strong magnetic coupling between the two phases, and electrical transport measurements demonstrate the strong insulating behavior of the LFO–CFO composite, which is found to be governed by Mott-variable range hopping conduction mechanisms. A shift in the Raman modes in the composite sample compared to those of pure CFO suggests the existence of strain-mediated elastic coupling between the two phases in the composite sample. Our work offers ordered composite nanowires with strong interfacial coupling between the two phases that can be directly integrated for developing multiphase spin insulatronic devices and emergent magnetic interfaces.

Highlights

Magnetic insulators[1] are emerging materials for inducing novel attributes into spintronics, magnonics, and spin insulatronics,[2] developing charge-neutral magnetic interfaces
We report an innovative synthesis approach utilizing the advantages of both bottom-up and top-down components for fabricating highly ordered arrays of LaFeO3 (LFO)−CoFe2O4 (CFO) bimagnetic composite nanowires
We demonstrated a novel approach for the fabrication of biphasic magnetic nanowires of LFO−CFO insulating nanocomposites by combining top-down and bottom-up approaches

Summary

INTRODUCTION

Magnetic insulators[1] are emerging materials for inducing novel attributes into spintronics, magnonics, and spin insulatronics,[2] developing charge-neutral magnetic interfaces. A classic example is yttrium iron garnet,[3] which has been studied for its low damping magnon transport, as well as for inducing proximity effects.[4] More recent studies have shown that other classes of ferrimagnetic insulators, in particular, spinel ferrites, can offer advantages over garnets, for example, a less complex crystal structure, lower synthesis temperature, and better compatibility with other crystalline materials.[5] On the other hand, today multifunctional composite materials[6] are unique in this context, primarily because of their capability to incorporate the desired properties of the individual components This results in a tailor-made end material that can be engineered for specific applications via introducing a wide variety of correlated phenomena. We first present the details of the fabrication of the composite nanowires, followed by their structural, magnetic, and electrical transport characterization

SYNTHESIS AND EXPERIMENTAL TECHNIQUES

RESULTS AND DISCUSSION

CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES