Spin Dynamical Properties of the Layered Perovskite La1.2Sr1.8Mn2O7

TL;DR

This study investigates the spin wave properties of La1.2Sr1.8Mn2O7, revealing its nearly two-dimensional dispersion and significant interlayer coupling, which are crucial for understanding its colossal magnetoresistance behavior.

Contribution

It provides detailed measurements of spin wave dispersion and coupling in La1.2Sr1.8Mn2O7, highlighting the effects of low dimensionality on magnetic properties.

Findings

Spin wave dispersion is nearly two-dimensional.

In-plane spin stiffness constant D ~ 151 meV·A.

Interlayer coupling is about 30% of in-plane coupling.

Abstract

Inelastic neutron-scattering measurements were performed on a single crystal of the layered colossal magnetoresistance (CMR) material La1.2Sr1.8Mn2O7 (Tc ~ 120K). We found that the spin wave dispersion is almost perfectly two-dimensional with the in-plane spin stiffness constant D ~ 151meVA. The value is similar to that of similarly doped La1-xSrxMnO3 though its Tc is three times higher, indicating a large renormalization due to low dimensionality. There exist two branches due to a coupling between layers within a double-layer. The out-of-plane coupling is about 30% of the in-plane coupling though the Mn-O bond lengths are similar.