High pressure neutron scattering of the magnetoelastic Ni-Cr Prussian blue analogue

TL;DR

This study investigates how applying pressure up to 0.6 GPa affects the crystal and magnetic structure of NiCrPB, revealing pressure-induced isomerization of cyanide ligands that impacts magnetic susceptibility.

Contribution

It provides detailed neutron diffraction data showing pressure-induced structural changes and ligand isomerization in NiCrPB, linking these to magnetic property modifications.

Findings

Pressure modifies the nuclear crystal structure of NiCrPB.

Cyanide isomerization under pressure affects local magnetic anisotropy.

Magnetic susceptibility decreases significantly under pressure.

Abstract

This paper summarizes 0 GPa to 0.6 GPa neutron diffraction measurements of a nickel hexacyanochromate coordination polymer (NiCrPB) that has the face-centered cubic, Prussian blue structure. Deuterated powders of NiCrPB contain ~100 nm sided cubic particles. The application of a large magnetic field shows the ambient pressure, saturated magnetic structure. Pressures of less than 1 GPa have previously been shown to decrease the magnetic susceptibility by as much as half, and we find modifications to the nuclear crystal structure at these pressures that we quantify. Bridging cyanide molecules isomerize their coordination direction under pressure to change the local ligand field and introduce inhomogeneities in the local (magnetic) anisotropy that act as pinning sites for magnetic domains, thereby reducing the low field magnetic susceptibility.