Local structures and local exchange interactions in doped magnetic materials of different dimensionality

TL;DR

This study uses neutron spectroscopy to explore how defects affect local exchange interactions and atomic distances in doped magnetic materials across different dimensionalities, revealing stepwise variations and decay patterns.

Contribution

It provides detailed experimental insights into local exchange interactions and atomic displacements around defects in one-, two-, and three-dimensional magnetic compounds.

Findings

Local exchange interactions deviate up to 10% from the average.

Local Mn-Mn distances vary stepwise with chemical pressure.

Displacement decay follows 1/r^2, 1/r, or remains constant depending on dimensionality.

Abstract

Defects intentionally introduced into magnetic materials often have a profound effect on the physical properties. Specifically tailored neutron spectroscopic experiments can provide detailed information on both the local exchange interactions and the local distances between the magnetic atoms around the defects. This is demonstrated for manganese dimer excitations observed for the magnetically diluted three-, two- and one-dimensional compounds KMnxZn1-xF3, K2MnxZn1-xF4 and CsMnxMg1-xBr3, respectively, with x=0.10. The resulting local exchange interactions deviate up to 10% from the average, and the local Mn-Mn distances are found to vary stepwise with increasing internal chemical pressure due to the Mn/Zn or Mn/Mg substitution. Our analysis qualitatively supports the theoretically predicted decay of atomic displacements according to 1/r**2, 1/r and constant (for three-, two- and one-dimensional compounds, respectively) where r denotes the distance of the displaced atoms from the defect.