Competition between two antiferromagnetic phases in Fe_xNbS₂ studied through coherent resonant scattering

The Fe-intercalated transition metal dichalcogenide Fe_xNbS₂ exhibits a highly tunable antiferromagnetic (AFM) ground state as a function of Fe intercalation ratio (x) near 1/3 [1]. The ground state transitions between two distinct phases: a stripe-AFM phase and a zigzag-AFM phase [2]. Remarkably, at an intermediate doping these two phases coexist and compete as a function of temperature [2]. We asked: how do these two electronic orders compete and evolve in real space within the same material?

During phase competition, the two phases adjust their real-space distributions based on their interaction and relative stability. We focus on whether the competing phase emerges from regions of weak order parameters, such as disordered areas and boundaries in the phase texture, or from regions with strong order parameters, like a topological defect seeded from within the core of an ordered domain. These scenarios suggest distinct real-space phase texture evolution, which we probe using coherent resonant scattering. This technique encodes real-space electronic domain patterns into speckle patterns observed on the Bragg peaks in Fourier space. We analyze the evolution of these speckle patterns, establishing a connection between the two AFM phases in Fe_xNbS₂ and highlight the unique capability of coherent resonant scattering to study competing and coexisting electronic ground states for the first time.

[1] Sci. Adv. 7, eabd8452 (2021)

[2] Phys. Rev. X 12, 021003 (2022)