Study of Magnetic Structure and Magnetic Fluctuations in Cr4.74Te8 Single Crystals

There is extraordinary interest in developing metallic 2D van der Waals materials that exhibit ferromagnetism (FM) with perpendicular magnetic anisotropy. Cr_4.74Te₈ is one such system whose structure consists of layers of CrTe₂ with extra Cr intercalated between them and it exhibits FM below T_c=160K. CrTe₂ itself is known to be a strong ferromagnet up to room temperature [1]. Adding the intercalated Cr introduces additional magnetic interactions between the van der Waals layers. Recently it was reported that Cr_4.74Te₈ exhibits a large (10%) negative magneto-resistance effect above T_c, over a temperature range of 30K [2]. Neutron diffraction measurements performed on the CORELLI instrument at the Spallation Neutron Source reveal the presence of a modulated short-range magnetic phase with a wave vector perpendicular to the van der Waals layers and a period that is commensurate with three times the c-axis length. The existence of this modulated phase appears over the same 30K temperature range that is observed in the magneto-transport measurements. The results will be discussed in terms of the magnetic coupling that is introduced from the intercalated Cr layers.