Ferromagnetic Cd(1-x)CuxCr2S4 thin films: Synthesis, characterization, and first-principles calculations

The magnetic chromium-based chalcogenide spinel system has been proposed for development of a new class of spintronic devices. They have been extensively investigated because of their unique electrical, magnetic, and optical properties. For example, CdCr ₂S ₄ is a well-established ferromagnetic semiconductor, while CuCr ₂S ₄ is a ferromagnetic metal. Their solid solution, Cd _(1-x)Cu _xCr ₂S ₄, offers an exciting possibility to tailor the magnetic and optical properties. In bulk form, they exhibit ferrimagnetic ordering with Curie temperature of about 85 K (for x = 0.1). However, thin films of these mixed magnetic chalcospinels materials have not been investigated. We have deposited Cd _(1-x)Cu _xCr ₂S ₄ thin films using a versatile and simple chemical spray deposition (CSD) method combined with post-annealing in a sulfur atmosphere. The Cd _(1-x)Cu _xCr ₂S ₄ thin films are deposited over a range of 0 ≤ x ≤ 0.2 using simple inorganic salts of Cd, Cu, and Cr. Systematic changes in the unit cell volume, lattice parameter, bandgap, and magnetic properties are observed with Cu incorporation. A decrease in the saturation magnetic moment and transition temperature ( T _c) are noted with increasing Cu substitution. First principles spin-polarized calculations within GGA and PBE approximation have been performed to determine the electronic and magnetic structure as a function of composition. The results suggest that an antiparallel alignment between Cu and Cr spins decreases the magnetization with increasing Cu substitution. The theoretical results are in qualitative agreement with the experimental findings and highlight the development of Cd _(1-x)Cu _xCr ₂S ₄ (0 ≤ x ≤ 0.2) thin films with tunable magnetic and semiconducting properties.