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Herein, using density functional theory, novel two-dimensional (2D) CrInX2 (X = S, Se, Te) structures are predicted to be practical ferromagnetic (FM) semiconductors. Phonon vibrations and molecular dynamics simulations verified their structural and thermodynamic stability. Sizable fully spin-polarized band gaps of 1.03 and 0.69 eV are found for CrInS2 and CrInSe2, while CrInTe2 exhibits half-metallic band nature (at 0 K with a perfect lattice). The high magnetic anisotropy energies are responsible for their long-range spin polarization. The Curie temperatures (Tc) are estimated to be 347, 397 and 447 K for CrInS2, CrInSe2 and CrInTe2, respectively, all well above the room-temperature. The high Tc originates from unusual FM direct exchange, the efficient super-exchange coupling between neighboring Cr eg-orbitals with zero virtual exchange gaps and the presence of dual Cr–X–Cr super-exchange channels. Our systematic study of the CrInX2 monolayer suggests that it could be a promising material for spintronics applications. [ABSTRACT FROM AUTHOR]

In recent years, the potential applications of two-dimensional (2D) metal-organic framework (MOF) materials in fields like spintronics have drawn increasing attention. Inspired by the successful synthesis of a perthiolated coronene (PTC)-Fe MOF structure, this study explores the fine-tuning of its electronic and magnetic structure by substituting Fe elements with various transition metals. Our calculations demonstrate a substantial increase in the Curie temperature ( T c ) by a factor of 5 for Co and 10 for Mn when replacing Fe. This enhancement is attributed to the elevated electron density near the Fermi level, facilitating the generation of additional itinerant electrons crucial for the Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange mechanism. However, substituting Fe with V, Cr, Ni, and Cu leads to a loss of ferromagnetic ground state. Our work enhances the understanding of the electronic and magnetic behavior of the 2D PTC-TM (transition metal) MOF family, and provides a promising avenue for engineering 2D magnetic MOF systems.

Herein, using density functional theory, novel two-dimensional (2D) CrInX 2 (X = S, Se, Te) structures are predicted to be practical ferromagnetic (FM) semiconductors. Phonon vibrations and molecular dynamics simulations verified their structural and thermodynamic stability. Sizable fully spin-polarized band gaps of 1.03 and 0.69 eV are found for CrInS 2 and CrInSe 2 , while CrInTe 2 exhibits half-metallic band nature (at 0 K with a perfect lattice). The high magnetic anisotropy energies are responsible for their long-range spin polarization. The Curie temperatures ( T c ) are estimated to be 347, 397 and 447 K for CrInS 2 , CrInSe 2 and CrInTe 2 , respectively, all well above the room-temperature. The high T c originates from unusual FM direct exchange, the efficient super-exchange coupling between neighboring Cr e g -orbitals with zero virtual exchange gaps and the presence of dual Cr-X-Cr super-exchange channels. Our systematic study of the CrInX 2 monolayer suggests that it could be a promising material for spintronics applications.

The second harmonic generation (SHG) responses of the paraelectric and ferroelectric phases of KH 2 PO 4 (KDP) were calculated by first-principles density functional theory (DFT) calculations, and the individual atom contributions to the SHG responses were analyzed by the atom response theory (ART). We show that the occurrence of static polarization does not enhance the SHG responses of the ferroelectric KDP, and that the Kleinman symmetry is reasonably well obeyed for the paraelectric phase, but not for the ferroelectric phase despite that the latter has a larger bandgap. This is caused most likely by the fact that the ferroelectric phase has lower-symmetry local structures than does the paraelectric phase. The contribution to the SHG response of an individual K + ion is comparable to that of an individual O 2- ion. The contributions of the O 2- and K + ions arise overwhelmingly from the polarizable parts of the electronic structure, namely, from the valence bands of the O-2p nonbonding states and from the conduction bands of the K-3d states., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)