Electro-Magnetic Behavior of Highly Correlated Fluorides KFeF₃, KCoF₃and KNiF₃: A ComparativeAb-initioStudy of Cation Effect

Abstract

Fluorides-based perovskites are currently the typical materials being used in spintronic devices, optoelectronic and magneto-resistance colossal fields. Solar cells made of Fluoro-perovskite hold much promise for the future of solar energy. The electronic structure and magnetic properties of KFeF3, KCoF3 and KNiF3 Fluorides are studied using ab initio Calculation. We have analysed the structural phases, total and partial electronic densities and band structures within the (DFT) vs the DFT+U description. We show the Electro-Magnetic Behavior using L(S)DA+U vs L(S)DA in a comparative study of cation effect by integrating three types of crystal structures (Cubic (Pm-3m), Four-Layered Hexagonal (P6/mmc), and Orthorhombic (Pnma)). Equilibrium lattices agree very well with experimental and theoretical data. Magnetic moment of each phase is discussed. The obtained results confirmed that the three crystal structures invested here exhibit Ferromagnetic (FM) behavior. The introduction of the Hubbard’s parameter U increases lattice parameters and magnetic moment. We deduce that the second cation plays an important role in the magnetic effects. L(S)DA+U show correctly that KFeF3, KCoF3 and KNiF3 are insulators.

Pressure dependence of the crystal-field spectrum of KNiF3 : Single and double excitations

“…The accuracy of this method is worthwhile to predict the pressure coefficient for those peaks whose pressure coefficients could not be measured due to experimental impediments. The present spectroscopic results enable us to determine the 10Dq dependence on R Ni−F from the KNiF 3 bulk modulus K 0 = 84(1) GPa, derived from acoustic measurements [18,19], and compare it with those obtained by DFT methods [9,14,15,17]. On the basis of potential law dependence of 10Dq with R Ni-F as 10Dq = CR −n Ni-F , we can obtain the exponent of this potential law from the pressure dependence of 10Dq:…”

“…Besides, KNiF 3 has been taken together with other fluoroperovskites KBF 3 as a prototype system to check the suitability of DFT methods to calculate structural properties mainly related to the equation of state and elastic constants [9,10,[12][13][14][15][16]. In spite of it, different values of the bulk modulus ranging from 60 to 115 GPa have been recently reported in KNiF 3 [9,10,17,18], showing important discrepancies with the experimental value derived from acoustic measurements of K 0 = 84 GPa [18,19]. It shows also important differences with bulk moduli obtained from the experimental V(P) data in isostructural KCoF 3 (K 0 = 117 GPa) [20,21], KMnF 3 (K 0 = 59 GPa) [22], or KZnF 3 (K 0 = 78 GPa) [23].…”