Ferromagnetism in Defected TMD Monolayer and Its Sustainability under O[sub.2], O[sub.3], and H[sub.2]O Gas Exposure: DFT Study

• Published in: Nanomaterials (Basel, Switzerland) Switzerland), 2023-05, Vol.13 (10)
• Main Authors: Devi, Anjna, Dhiman, Neha, Kumar, Narender, Alfalasi, Wadha, Kumar, Arun, Ahluwalia, P. K, Singh, Amarjeet, Tit, Nacir
• Format: Article
• Language: English
• Subjects: Ferromagnetism; Magnetic properties; Optical properties; Sustainable development; Volatile organic compounds
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano13101642

Spin-polarized density-functional theory (DFT) has been employed to study the effects of atmospheric gases on the electronic and magnetic properties of a defective transition-metal dichalcogenide (TMD) monolayer, MoX[sub.2] with X = S or Se. This study focuses on three single vacancies: (i) molybdenum "V[sub.Mo]"; (ii) chalcogenide "V[sub.X]"; and (iii) di-chalcogenide "V[sub.X2]". Five different samples of sizes ranging from 4 × 4 to 8 × 8 primitive cells (PCs) were considered in order to assess the effect of vacancy-vacancy interaction. The results showed that all defected samples were paramagnetic semiconductors, except in the case of V[sub.Mo] in MoSe[sub.2], which yielded a magnetic moment of 3.99 μ[sub.B] that was independent of the sample size. Moreover, the samples of MoSe[sub.2] with V[sub.Mo] and sizes of 4 × 4 and 5 × 5 PCs exhibited half-metallicity, where the spin-up state becomes conductive and is predominantly composed of d[sub.xy] and d[sub.z2] orbital mixing attributed to Mo atoms located in the neighborhood of V[sub.Mo]. The requirement for the establishment of half-metallicity is confirmed to be the provision of ferromagnetic-coupling (FMC) interactions between localized magnetic moments (such as V[sub.Mo]). The critical distance for the existence of FMC is estimated to be d[sub.c]≅ 16 Å, which allows small sample sizes in MoSe[sub.2] to exhibit half-metallicity while the FMC represents the ground state. The adsorption of atmospheric gases (H[sub.2]O, O[sub.2], O[sub.3]) can drastically change the electronic and magnetic properties, for instance, it can demolish the half-metallicity characteristics. Hence, the maintenance of half-metallicity requires keeping the samples isolated from the atmosphere. We benchmarked our theoretical results with the available data in the literature throughout our study. The conditions that govern the appearance/disappearance of half-metallicity are of great relevance for spintronic device applications.