  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.
