Griffiths-like phase, large magnetocaloric effect, and unconventional critical behavior in the NdSrCoFeO6 disordered double perovskite

Magnetoelastic Coupling and Cryogenic Magnetocaloric Effect in Two-Site Disordered GdSrCoFeO6 Double Perovskite

“…However, in our case, the M 2 vs H / M curves shown in the inset of Figure a do not exhibit this behavior, indicating that the mean-field model cannot characterize the critical trend of GdSrCoFeO 6 . The 3D Ising model (β = 0.325, γ = 1.24), 3D Heisenberg model (β = 0.365, γ = 1.386), tricritical mean-field model (β = 0.25, γ = 1.0), and 3D XY model (β = 0.345, γ = 1.316) were also tested, as exhibited in Figure S5, but neither describes well the critical behavior of GdSrCoFeO 6 . Hence, a MAP should be employed to obtain the critical exponents.…”

“…The magnetic properties are associated with the spin polarization of Gd and the short- and long-range competitions created by the different intensities of magnetic moments at the Co and Fe sites, while the electronic characteristics depend on crossings of spin states in the Co ions, facilitated by a crystal field splitting that allows electron transfers to the e.g. level, and by the oxygen-intermediated Co and Fe double exchange interaction . Moreover, the Co average magnetic moment is slightly lower for the FiM than for the FM structure, indicating the electronic behavior of GdSrCoFeO 6 is sensitive to the Co magnetic moment intensity.…”

“…We consider the U eff = U-J effective potential term in accordance with the method by Anisimov et al After testing different values for the Hubbard U eff parameter, we use 6.0 eV to describe the Gd-4 f strong correlated electrons and 4.0 eV for the 3 d -states of Co and Fe ions. The choice of the GGA + U beyond DFT standard calculations was motivated by our successful description of the structural, magnetic, and electronic characteristics of NdSrCoFeO 6 . The calculations were successfully converged in energy (10 –5 Ry) and charge (10 –5 eV/bohr) criteria, and the relaxation process of the internal parameters ended when the forces between the atoms were less than 2mRy/bohr.…”

“…level, and by the oxygen-intermediated Co and Fe double exchange interaction. 40 Moreover, the Co average magnetic moment is slightly lower for the FiM than for the FM structure, indicating the electronic behavior of GdSrCoFeO 6 is sensitive to the Co magnetic moment intensity. The Gd rare earth ion also influences the related resonant magnetic and electronic process since the difference between the calculated FiM and FM magnetic orders is the spin projection on the Gd atoms.…”

“…DFT Studies. To further investigate the electronic and magnetic characteristics of the GdSrCoFeO 6 , DFT calculation was performed based on a GGA + U fully optimized cell with 40 where we demonstrated that the rock salt-like structure illustrated in Figure 9 is the closest to the description of a real system. Additionally, we computed different spin-magnetic configurations for the GdSrCoFeO 6 structure, where the minimum interaction energy was obtained for the FiM and FM ordering.…”