Investigating the Structural and Magnetic Properties of CrxTaS2 when x ≤ 0.25

Moore’s Law states that the number of transistors in an integrated circuit will double approximately every two years. Although this trend has held steady since the mid-twentieth century, in the past decade, it was observed that new technologies are needed to maintain this growth while minimizing energy consumption. A promising avenue to address this issue is the field of spintronics, which take advantage of an additional degree of freedom, that is spin, as a way to store and retrieve information.<br/>We propose that Cr-intercalated TaS2 (CrxTaS2) is a promising material for spintronics due to its unique structural and magnetic properties. CrxTaS2 has a layered structure containing Cr3+ions between two-dimensional sheets of TaS2. Typically, TaS2is a nonmagnetic material, but when spin-bearing Cr3+ ions are introduced between layers, the resultant material becomes magnetic. Layered magnets present an exciting alternative to current materials, as one can tune their magnetic properties based on intercalant stoichiometries. Preliminary data shows that when x = 0.25, the Cr intercalants order structurally in a 2 x 2 superlattice, and the material enters a spin glass state below 100 K. A spin glass is a magnetic state in which competition between ferromagnetic (FM) and antiferromagnetic (AFM) interactions causes spins to order randomly.<br/>Several spintronic device designs utilize spin glasses interfaced with FMs or AFMs. Therefore, materials with tunable spin glass properties that can form clean interfaces with other magnetic materials are highly desired. We hypothesize that as the Cr amount decreases below 0.25, the material will exhibit more disorder and glassy behavior.<br/>We aim to study how varying intercalant stoichiometry affects the magnetic and structural properties of CrxTaS2. Three batches of crystals were grown using chemical vapor transport, targeting stoichiometries of 0.25, 0.20, and 0.15. Cr ratios were then confirmed using energy-dispersive X-ray spectroscopy (EDX). Raman spectroscopy was used to probe the structures of the crystals. The x = 0.25 crystals contained a feature at 156 cm-1, demonstrating an ordered 2 x 2 superlattice. However, in the x = 0.20 crystals, this feature was red-shifted, suggesting the presence of a defective superlattice.<br/>The x = 0.15 crystals grew in the expected hexagonal shape, but the Raman spectra were highly disordered. Golden-tinted, ribbon-like crystals were also obtained, which appear to be a side product based on Raman, EDX, and morphology.<br/>Thus, we predict that lower Cr intercalant crystals may have transition temperatures lower than 100K due to enhanced disorder. The results of the x = 0.25 stoichiometry of Cr hold promise for application in next-generation devices. Further structural and magnetic characterization on stoichiometries consisting of x &lt; 0.25 will unveil how these crystals can be tuned to our needs by varying the compositions.