The coexistence of different properties in the same material often results in exciting physical effects. At low temperatures, the pyrite transition-metal disulphide NiS2 hosts both antiferromagnetic and weak ferromagnetic orders, along with surface metallicity dominating its electronic transport. The interplay between such a complex magnetic structure and surface-dominated conduction in NiS2, however, is still not understood. A possible reason for this limited understanding is that NiS2 has been available primarily in bulk single-crystal form, which makes it difficult to perform studies combining magnetometry and transport measurements with high spatial resolution. Here, NiS2 nanoflakes are produced via mechanical cleaving and exfoliation of NiS2 single crystals and their properties are studied on a local (micron-size) scale. Strongly field-asymmetric magnetotransport features are found at low temperatures, which resemble those of more complex magnetic thin film heterostructures. Using nitrogen vacancy magnetometry, these magnetotransport features are related to exchange-bias-type effects between ferromagnetic and antiferromagnetic regions forming near step edges at the nanoflake surface. Nanoflakes with bigger steps exhibit giant magnetoresistance, which suggests a strong influence of magnetic spin textures at the NiS2 surface on its electronic transport. These findings pave the way for the application of NiS2 nanoflakes in van der Waals heterostructures for low-temperature spintronics and superconducting spintronics.
Bibliographical noteFunding Information:
R. H. and A. D. B. acknowledge funding from the Alexander von Humboldt Foundation in the framework of a Sofja Kovalevskaja grant and from the Zukunftskolleg at the University of Konstanz. A. D. B and E. S. also acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG) through the SPP 2244 priority programme (grant No. 443404566). M. Am. acknowledges financial support from the Ministerio de Ciencia, Innovación y Universidades of Spain and FEDER (ERDF: European Regional Development Fund) under the research grant No. PID2019-106820RB-C21/22 and FEDER/Junta de Castilla y León grant No. SA121P20. Work performed at the University of Cambridge was supported by the Cambridge Nanoscale Sensing and Imaging Suite (CANSIS) as part of the Cambridge Henry Royce Institute under Engineering and Physical Sciences Research Council (EPSRC) grant No. EP/P024947/1 and from EPSRC QUES2T (EP/N015118/1). A. K. C. T. acknowledges funding from A*STAR through the National Science Scholarship. M. H. acknowledges funding from EPSRC NQIT (EP/M013243/1). S. E. K. acknowledges support from the American University of Sharjah under the FRG2020-M-S138 grant. Work at the University of Minnesota was supported by the US Department of Energy through the University of Minnesota Center for Quantum Materials under grant No. DE-SC0016371.
© 2023 The Royal Society of Chemistry.
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