The Superexchange Mechanism in Crystalline Compounds: The Case of KMF3 (M=Mn, Fe, Co, Ni) Perovskites


Roberto Dovesi
Department of Chemistry, University of Turino, Via P. Giuria 5, 10125 Torino
Fabien Pascale
University of Lorraine, Nancy, CNRS, Laboratoire de Physique et Chimie Th´eoriques, UMR 7019, Vandoeuvre-les-Nancy
Philippe D’Arco
Sorbonne University, CNRS-INSU, Institut des Sciences de la Terre, ISTeP UMR 7193, F-75005 Paris
Francesco Gentile
Dipartimento di Ingengeria Chimica, dei Materiali e delle Produzioni Industriali DICMAPI, Universit`a degli Studi di Napoli Federico II, Piazzale Vincenzo Tecchio 80, 80125, Napoli
Valentina Lacivita
Samsung Semiconductors Inc., Advanced Materials Lab, 10 Wilson Rd., Cambridge, MA 02138


The ferromagnetic and antiferromagnetic wavefunctions of four KMF3 (M= Mn, Fe, Co and Ni) perovskites have been obtained quantum-mechanically with the CRYSTAL code, by using the Hartree-Fock (HF) Hamiltonian and three flavours of DFT (PBE, B3LYP and PBE0) and an all- electron Gaussian type basis set. In the Fe and Co cases, with d6 and d7 occupation, the Jahn Teller distortion of the cubic cell is as large as 0.12 ˚A. Various features of the superexchange interaction energies (SIE), namely additivity, dependence on the M-M distance, on the M^F M angle, and on the adopted functional, are explored. The effect of SIE on the equilibrium geometry and volume of the unit cell is discussed, and it is shown that the key quantity is the spin polarization of the (closed shell) F ions along the M-F-M path. The effect of this magnetic pressure is evaluated quantitatively for the first time.

March 8, 2022