Investigation of X2CdS4 (X=Dy, Tm) spinels for energy harvesting and spintronic applications

The structural, electronic, magnetic, optical, and thermoelectric (TE) features of X2CdS4 (X ​= ​Dy, Tm) spinels are investigated by using the full potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). The stability of both materials is verified by the negative values of formation enthalpy (ΔHf) and tolerance factor. Both spinels are semiconductors with band gap (Eg) of 0.9/1.2 eV in spin up/down channels of Dy2CdS4, while Tm2CdS4 exhibits Eg of 1.04/0.80 eV in spin up/down channel. The calculated magnetic moments (μB) of spinels Dy2CdS4 and Tm2CdS4 are 19.000 and 8.00 ​μB, correspondingly. Optical features including absorption coefficient α(ω), refractive index n(ω), dielectric constants ε(ω), optical conductivity σ(ω), reflectivity R(ω), and extinction coefficient k(ω) are investigated. Both spinels X2CdS4 (X ​= ​Dy, Tm) discover the maximum photon absorption in the ultraviolet area, which proves that both are acceptable for usage in sensors, optical filters, and optoelectronic applications. BoltzTrap code is utilized to discover TE features like electrical conductivity (σ/τ), Seebeck coefficient (S), thermal conductivity (k/τ), power factor (PF) and figure of merit (ZT). Outcomes of this work enlighten the promising applications of studied spinel compounds in spintronic, optical and TE devices. The stability of both materials is verified by the negative values of formation enthalpy (ΔHf) and tolerance factor. Both Dy2CdS4 and Tm2CdS4 are semiconductors with a direct bandgap (Eg) of 0.9 in spin (↑) up and 1.2 ​eV in spin (↓) down for Dy2CdS4 while 1.04 in spin (↑) and 0.80 ​eV in spin (↓) for Tm2CdS4. The calculated magnetic moments (μB) of spinels Dy2CdS4 and Tm2CdS4 are 19.000 and 8.00 ​μB, correspondingly. Outcomes of this work enlighten the promising applications of studied spinel compounds in spintronic, optical and TE devices. [Display omitted] •The stability of X2CdS4 (X ​= ​Dy, Tm) materials is verified by ΔHf.•Both Dy2CdS4 and Tm2Cd S4 are semiconductors with a direct bandgap (Eg).•The calculated magnetic moments of spinels Dy2CdS4 and Tm2CdS4 are 19.000 and 8.00 ​μB, respectively.•Optical features reveal the maximum photon absorption in the ultraviolet region.•Outcomes enlighten the applications of studied spinels in spintronic, optical and TE gadgets.