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

Abstract

This paper summarizes 0 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 $\ensuremath{\approx}100$-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.