Diagonal and Collinear Incommensurate Spin Structures in underdoped La$_{2-x}$Ba$_{x}$CuO$_{4}$

TL;DR

This study reveals how incommensurate spin structures in underdoped La-Ba-Cu-O vary with doping, showing a rotation from diagonal to collinear order associated with the transition from insulator to superconductor.

Contribution

It demonstrates the doping-dependent rotation of static incommensurate spin order in La-Ba-Cu-O, linking magnetic structure changes to electronic phase transitions.

Findings

Static incommensurate magnetic order observed in x=0.05 and 0.025 samples.

Rotation of spin ordering wavevectors by 45 degrees with doping.

Spin modulations are one-dimensional and aligned along orthorhombic b* direction.

Abstract

We have studied incommensurate spin ordering in single crystal underdoped La_{2-x}Ba_{x}CuO_{4} with x~0.08, 0.05 and 0.025 using neutron scattering techniques. Static incommensurate magnetic order is observed in the La_{2-x}Ba_{x}CuO_{4} (x=0.05 and 0.025) compounds with ordering wavevectors which are rotated by 45 degree about the commensurate (0.5,0.5,0) position, with respect to that in the superconducting x=0.08 material. These spin modulations are one dimensional in the x=0.05 and 0.025 samples, with ordering wavevectors lying along the orthorhombic b* direction. Such a rotation in the orientation of the static spin ordering as a function of increasing Ba doping, from diagonal to collinear, is roughly coincident with the transition from an insulating to a superconducting ground state and is similar to that observed in the related La_{2-x}Sr_{x}CuO_{4} system. This phenomenon is therefore a generic property of underdoped La-214 cuprates.