Incommensurate charge and spin density wave order in electron doped SrMn1-xWxO3 (x= 0.08 to 0.1875)

TL;DR

This study reveals how electron doping in SrMn1-xWxO3 induces incommensurate charge and spin density wave orders, with structural and magnetic phases evolving with doping levels, sharing similarities with high-Tc cuprates.

Contribution

It provides the first detailed neutron diffraction analysis of incommensurate charge and spin density waves in electron-doped SrMn1-xWxO3, highlighting the relationship between orbital order and electronic instabilities.

Findings

Incommensurate charge order correlates with 3dx2-y2 orbital order.

Multiple antiferromagnetic phases emerge with doping levels.

Incommensurate SDW order appears at higher doping, with evolving propagation vectors.

Abstract

Incommensurate (IC) charge-order (CO) and spin density wave (SDW) order in electron doped SrMn1-xWxO3-{\delta} (x= 0.08 to 0.1875) have been studied using neutron diffraction.The study highlights the drastic effect of electron doping on the emergence of magnetic ground states which were not revealed in manganites before. With increasing (x) the crystal structure changes from simple tetragonal (P4/mmm) to an IC-CO modulated structure with super space-group P2/m({\alpha}\b{eta}0)00 having ab-planer ferro order of 3dx2-y2 orbitals in a compressed tetragonal (c<a) lattice. The IC-CO order is found to be intimately related with the 3dx2-y2 orbital order.The occurrence of IC-CO has been attributed to the mixed character (itinerant/localized) of eg-electrons undergoing Fermi-surface nesting of 3dx2-y2 band causing electronic instability, which opens a gap through a charge density wave (CDW) mechanism. This feature appears to share proximity with the high-Tc cuprates. At lower temperatures, the CDW phase undergoes SDW transition, which changes continuously with x and finally disappear at higher x due to the introduction of large frustration into the system. For 0.08 < x < 0.10 a C-type antiferromagnetic (AFM) order with propagation vector k = (1/2, 1/2, 0) appears under ferro-ordering of 3dz2 orbitals, whereas for x > 0.1, a different C-type AFM order with propagation vector k = (1/2,0,1/2), coexists with an incommensurate SDW order with k = (0.12, 0.38, 1/2).For compositions with 0.1625 < x < 0.175, while the structural features of CDW and orbital-order remain qualitatively the same, the magnetic interaction gets modified and results another SDW phase with single incommensurate propagation vector k = (0.07, 0.43, 1/2). A detail magnetic and structural phase-diagram, as a function of W substitution for SrMn1-xWxO3 (0.08 < x < 0.4) is presented.