Electronic structure and magnetocaloric properties of Ce2Fe17−xCox compounds upon Co substitution

Abstract

Electronic structure, magnetic properties and magnetocaloric effect of Ce2Fe17−xCox alloys upon Co substitution have been systematically investigated. The Ce2Fe17−xCox (x = 0.33–1) crystallizes in a rhombohedral Th2Zn17-type 2:17 R main phase and minor CeFe2/α-Fe secondary phases. The Ce2Fe17−xCox shows a second-order phase transition characteristic and Co substitution contributes to the enhancement in the Curie temperature (TC) and the magnetocaloric properties. With x increasing from 0.33 to 1, the TC raises from 261.9 to 335.6 K, the maximum magnetic entropy change (ΔSMmax) at a field change of 0–2 T enhances by 14.9% from 2.28 to 2.62 J∙kg−1K−1, and the relative cooling power (RCP) increases from 164.8 to 171.3 J∙kg−1, respectively. According to first-principles calculations, Co atoms energetically occupy the 18h site and enhances the inter-site exchange coupling parameters (Jij) due to the strong hybridization and coupling between Co 3d and Fe 3d electrons. Furthermore, the spin-down total density of states (DOS) reveals a pseudogap developed across the Fermi level (EF) located at around − 0.09 – +0.20 eV with increasing Co content from 0.33 to 1. This pseudogap contributes to the stabilization of ferrimagnetic state and the improvement of the magnetic entropy change. Understanding the underlying electronic and magnetic behavior mechanisms is helpful for developing high-performance magnetocaloric materials.