Abnormal thickness-dependent magneto-transport properties of vdW magnetic semiconductor Cr 2 Si 2 Te 6

Cr 2 Si 2 Te 6 (CST) is a van der Waals (vdW) ferromagnetic semiconductor. The unique spin model and temperature-dependent magnetic ordering of CST provide opportunities for the next generation of two-dimensional (2D) spintronic devices. Here, abnormal magneto-transport properties are found in CST nanoflakes with variations in thickness. Interestingly, the thickness-dependent magnetoresistance (MR) effect exhibits a nonlinear change as a function of the magnetic field, temperature, and thickness. At a certain temperature below Curie temperature ( T c ), a sign reversal of MR ratio from positive to negative can even be detected with thickness reduction. At the temperature range from T c to 60 K, the Hall effect also presents a transformation from nonlinear behavior in thick layer CST to linear behavior in thin layer CST. These distinctive magneto-transport properties are attributed to the variation of spin correlation with thickness in CST nanoflakes. These findings probe the unique magneto-transport properties of CST and associate it with ferromagnetic correlation, which provides a basis for subsequent spintronics device design based on this material. This work also offers new insights into the relationship between sample thickness, transport properties, and spin correlation of other vdW ferromagnets. It lays a foundation for future vdW magnet-based device fabrication and possible spintronic applications.