Evidence of active role played by the nonmagnetic element Sr in magnetostructural coupling in ${\text{SrRuO}}_3$

We study the magnetic transition in ${\text{SrRuO}}_3$, the only itinerant $4d$ ferromagnet, employing x-ray absorption fine structure study and state-of-the-art band-structure calculations. Both experimental and theoretical results reveal an unusual evolution of the local structural parameters around the spectator element, Sr, across the magnetic transition. Interestingly, such evolution of the Sr-related bonds nucleate at a temperature, $T^{\star }$, higher than the magnetic transition temperature, indicating the presence of a precursor effect. Contrary to common belief, these results point to the active role played by the Sr ion in the magnetostructural coupling present in this compound.

Figure 1

(Color online) Crystal structure of ${\text{SrRuO}}_3$ forming in perovskite structure. ${\text{RuO}}_6$ units are shown by shaded octahedra. Sr atoms which sit in the hollow formed by corner-shared ${\text{RuO}}_6$ units, are shown by big circles. The oxygen atoms at the apical positions of the ${\text{RuO}}_6$ octahedra are labeled as O1 and those at the plane are labeled as O2.

Figure 2

(Color online) Fourier transform of the $k^2$-weighted XAFS data at different temperatures at (a) $\text{Ru}K$ edge and (b) $\text{Sr}K$ edge.

Figure 3

(Color online) Temperature dependence of the bond lengths (left column) and corresponding Debye-Waller factors (right column) for the structural units around Ru sites.

Figure 4

(Color online) Temperature dependence of the bond lengths (left panel) and corresponding DWF (right panel) for the structural units around the Sr site. The solid line in the bottom-most right panel represents the calculated Debye-Waller factor from correlated Debye model corresponding to the Debye temperature of 525 K.

Figure 5

(Color online) Wannier functions of the minimal set of $\text{O}2p$ NMTOs calculated for optimized geometries with magnetization off (left panel) and magnetization on (right panel). The orbital shapes (constant amplitude surfaces) with $\pm$ signs are labeled by red and blue colors, respectively.