Magnetic properties of LaO$_{1-x}$F$_x$FeAs

TL;DR

This study uses advanced first-principles calculations to explore how doping affects the magnetic and structural properties of LaOFeAs, revealing a transition in magnetic order and its persistence up to superconductivity onset.

Contribution

It provides detailed insights into the magnetic and structural evolution of LaOFeAs with doping, highlighting the transition from orthorhombic to other phases and magnetic order persistence.

Findings

Doping induces an orthorhombic ground state.

Magnetic structure transitions from commensurate to incommensurate between x=0.025 and x=0.04.

Magnetic order persists up to the superconducting critical doping of x=0.05.

Abstract

Using state-of-the-art first-principles calculations we have elucidated the complex magnetic and structural dependence of LaOFeAs upon doping. Our key findings are that (i) doping results in an orthorhombic ground state and (ii) there is a commensurate to incommensurate transition in the magnetic structure between $x=0.025$ and $x=0.04$. Our calculations further imply that in this system magnetic order persists up to the onset of superconductivity at the critical doping of $x=0.05$. Finally, our investigations of the undoped parent compound reveal an unusually pronounced dependence of the magnetic moment on details of the exchange-correlation (xc) functional used in the calculation. However, for all choices of xc functional an orthorhombic structure is found.