Mn-induced Fermi-surface reconstruction in the SmFeAsO parent compound

Abstract

The electronic ground state of iron-based materials is unusually sensitive to electronic correlations. Among others, its delicate balance is profoundly affected by the insertion of magnetic impurities in the FeAs layers. Here, we address the effects of Fe-to-Mn substitution in the non-superconducting Sm-1111 pnictide parent compound via a comparative study of SmFe$$_{1-x}$$ 1 - x Mn$$_{x}$$ x AsO samples with $$x(\text{Mn})=$$ x ( Mn ) = 0.05 and 0.10. Magnetization, Hall effect, and muon-spin spectroscopy data provide a coherent picture, indicating a weakening of the commensurate Fe spin-density-wave (SDW) order, as shown by the lowering of the SDW transition temperature $$T_\text{SDW}$$ T SDW with increasing Mn content, and the unexpected appearance of another magnetic order, occurring at $$T^{*} \approx 10$$ T ∗ ≈ 10 and 20 K for $$x=0.05$$ x = 0.05 and 0.10, respectively. We attribute the new magnetic transition at $$T^{*}$$ T ∗ , occurring well inside the SDW phase, to a reorganization of the Fermi surface due to Fe-to-Mn substitutions. These give rise to enhanced magnetic fluctuations along the incommensurate wavevector $$\varvec{Q}_2 =(\pi \pm \delta ,\pi \pm \delta )$$ Q 2 = ( π ± δ , π ± δ ) , further increased by the RKKY interactions among Mn impurities.

Magnetotransport as a probe for the interplay between Sm and Fe magnetism in SmFeAsO

“…Figure 1(b) shows the Hall coefficient R H extracted from Hall effect measurements between 0.3 and 150 K measured under standard conditions (with B applied parallel to the c-axis and the current applied in the ab-plane). Below T NFe , R H is negative and increases in absolute value with decreasing T and an abrupt upturn occurs below T NSm (see inset of figure 1(b)), suggesting a reorganization of the electronic bands, as already observed in similar systems [26,35].…”

“…Since Sm ordering survives the onset of SC in many SmFeAsO 1 − x F x compounds [16,18,19], these intriguing issues could be studied through in-plane and out-of-plane H c2 measurements down to low T to test the effects of Sm ordering on the superconducting state. This information is lacking due to the very high H c2 of SmFeAsO 1 − x F x compounds, which does not allow for a direct measurement down to low T. However, T c , and accordingly H c2 , can be progressively suppressed in SmFeAsO 1 − x F x compounds by partial substitution of Fe with d elements (Ru, Mn, Ni) [41,42] without affecting the Sm ordering [35]. Another possibility is to investigate Co-doped SmFeAsO compounds, which show maximum T c s of tens of K [43][44][45].…”