Comparative study between TB-mBJ and GGA+U on magnetic and optical properties of CdFe_2O_4

摘要

Full Potential Linearized Augmented Plane Wave (FP-LAPW) based on density functional theory (DFT) is carried out to study the density of states, optical properties and XMCD properties of bulk spinel ferrite CdFe_2O_4. The exchange correlation potential was solved by Generalized Gradient Approximation (GGA) that underestimates the band gap value, therefore, the later needed to be corrected using two approaches: Tran-Blaha modified Becke-Johnson exchange potential approximation (TB-mBJ) and GGA plus the multi-orbital mean-field Hubbard potential (GGA+U). These methods provide accurate results in good agreement for the optical properties and band gap with experimental data. CdFe_2O_4 has a coefficient of absorption more than 10~4/cm in the visible range. The first critical point known as optical absorption edge calculated with GGA+U and TB-mBJ appears at 1.56 eV and 1.88 eV, respectively. The XMCD spectra show a double pic in L_3 edge indicating the presence of both Fe~(2+) and Fe~(3+) ions, occupying the octahedral sites. However, using GGA+U the charge of the atoms is well localized and subsequently the double peak does not reproduce. The crystal field creates additional levels that provide radiation in the visible, having these properties; this compound promotes its use for device applications operating over a wide energy range based on CdFe_2O_4 in optoelectronics.