Noncollinear magnetic ground state of PrFeAsO

Abstract

Noncollinear magnetic investigations of the ground state in PrFeAsO have been performed by the density-functional theory. We calculated the total energy and made structure optimization, and the electronic density of states of PrFeAsO was analyzed. There are three different magnetic structures in PrFeAsO defined by experiments. Based on these magnetic structures, we studied four collinear and four noncollinear cases. The ground state is found to take the ordering proposed by Zhao, in which the FeAs plane is of stripe antiferromagnetism and Pr spins are perpendicular to Fe spins. The electronic density of states indicates that for PrFeAsO the increase of the electron Coulomb interaction leads to a decrease in conductivity.

Ab initiostudy on the rare-earth iron-pnictides RFeAsO (R = Pr, Nd, Sm, Gd) in the low-temperatureCmmaphase

“…The same increment of Fe magnetic moments was also reported for LaFeAsO [43,44]. Our results are in agreement with the previous calculations both for the Fe moments and the R moments [29,30]. However, the magnetic moments of Fe calculated with DFT overestimate the experimental measurements [45].…”

“…For the material PrFeAsO, our GGA/GGA + U total DOS and partial DOS results are in good agreement with the previous calculations of Alyahyaei and Jishi [28] with the same magnetic configuration and using similar effective Coulomb interaction values of U eff = 3 or 5 eV for Pr and U eff = 3.4 eV for Fe. In the study of Liu et al [29], they reported their density of state calculations within a non-collinear magnetic structure considering the effective Coulomb interaction parameters as U eff = 4 eV for Pr and U eff = 2 eV for Fe, and our results are also very similar to this non-collinear magnetic structure.…”

“…For structural geometry optimization, we have used the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm with threshold values of 0.001 Ryd au −1 and 10 −4 Ryd for residual forces and energy variation, respectively. For GGA + U calculations [36], the effective on-site Coulomb interaction parameters [37] are chosen as U eff = 5 eV for rare-earths and U eff = 2 eV and 3 eV for iron atoms, consistent with previous findings [24,[28][29][30].…”

“…Alyahyaei and Jishi [28], in their density functional theory (DFT) calculations with the generalized gradient approximation (GGA), have considered various possible magnetic orders for Fe and R ions in the materials CeFeAsO and PrFeAsO and found that, when including the on-site Coulomb interaction (GGA + U), the ground state magnetic moments have a stripe-like antiferromagnetic (AFM) order for Fe ions and a zigzag-like AFM order for the rare-earths. In the studies of [29,30], several collinear and non-collinear magnetic structures of PrFeAsO and CeFeAsO were investigated theoretically, exhibiting similar densities of states (DOS) in different magnetic configurations. The electronic properties of RFeAsO compounds with high-temperature P4/nmm structures were also investigated theoretically by considering rare-earth 4f states as core [31] or valence [32].…”

Magnetism of PrFeAsO parent compound for iron-based superconductors: Mössbauer spectroscopy study

“…Praseodymium orders antiferromagnetically within practically saturated SDW phase at about 12 K. Localized magnetic moments of praseodymium are oriented perpendicular to the Fe-As planes. A partial rotation of the praseodymium moments on the former tetragonal plane occurs at lower temperatures and it seems to be completed above 4.2 K. Antiferromagnetic order of praseodymium moments is preserved during this rotation [19][20][21][22]. One can expect small almost axially symmetric electric field gradient tensor on iron nuclei with the principal component being perpendicular to the Fe-As plane.…”