Exchange bias and topological Hall effect of Fe and Co intercalated NbS2 single crystals

Abstract

In recent years, the topological Hall effect generated by noncoplanar magnetic structures has been studied extensively. Some two-dimensional chalcogenides with 3d transition metal intercalations also exhibit similar properties. In this study, we investigated the crystalline structure and the magnetic and transport properties of Fe and Co codoped NbS2 single crystals. The structural results indicate disorder between the Fe and Co atoms within the interlayers of NbS2. Magnetic measurements showed that the vertical exchange bias effect appeared below the Néel temperature (TN), with a maximum value of approximately 2.5 mμB/f.u. at 2 K, which can be ascribed to the appearance of a spin-glass state. Additionally, accompanying the antiferromagnetic phase transition, nontrivial electrical transport properties were observed. Below TN, the magnetoresistance became positive and exhibited an initial increase, followed by a decrease with decreasing temperature. The Hall resistivity shows a hump-like curve near TN, indicating a topological Hall effect. This behavior is related to fluctuations in the spin chirality, which affects the scattering of charge carriers. Based on the correlation between the magnetoresistance and Hall resistivity responses, it is believed that the magnetic moments of the doped Fe and Co atoms in a single crystal compete with each other near the Néel temperature, resulting in complex magnetic structures such as noncoplanar and noncollinear arrangements. Such a two-dimensional antiferromagnetic material system provides an ideal platform for studying unconventional transport mechanisms.