Magneto-elastic coupling between copper spin configurations and oxygen octahedra in La(2-x)Sr(x)CuO(4). Untwinning, Raman (phonon) spectrum, and neutron response

TL;DR

This paper reveals how magneto-elastic coupling between copper spins and oxygen octahedra explains neutron and Raman spectroscopy results, magnetic-field induced untwinning, and magnetic periodicity in La(2-x)Sr(x)CuO(4).

Contribution

It introduces a magneto-elastic coupling model that unifies various experimental observations in La(2-x)Sr(x)CuO(4) and related compounds.

Findings

Magneto-elastic coupling modulates spin and lattice in different phases.

Explains magnetic-field induced untwinning in La(2-x)Sr(x)CuO(4).

Accounts for magnetic periodicity in La(2-x-y)Sr(x)Nd(y)CuO(4).

Abstract

We reinterpret neutron scattering and Raman spectroscopy experiments in La(2-x)Sr(x)CuO(4), showing modulation of spin and lattice degrees of freedom both in the low-temperature orthorhombic and tetragonal phases, in terms of a magneto-elastic coupling between noncollinear configurations for the copper spins and the oxygen octahedra. The magneto-elastic coupling furthermore explains the recently discovered magnetic-field induced untwinning in La(2-x)Sr(x)CuO(4), for x<2%, and allows us to understand why in La(2-x-y)Sr(x)Nd(y)CuO(4) with y=0.4 and x=1/8, for example, when (1,0) and/or (0,1) static spin spirals are stabilized due to hole frustration, the atomic modulation in the low-temperature tetragonal phase of La(2-x-y)Sr(x)Nd(y)CuO(4) has a periodicity of 4 lattice spacings, half the magnetic one.