Pressure effect on the magnetism and crystal structure of magnetoelectric metal–organic framework [CH3NH3][Co(HCOO)3]

Abstract

[CH₃NH₃][Co(HCOO)₃] is the first perovskite-like metal–organic framework exhibiting spin-driven magnetoelectric effects. However, the high-pressure tuning effects on the magnetic properties and crystal structure of [CH₃NH₃][Co(HCOO)₃] have not been studied. In this work, alongside ac magnetic susceptibility measurements, we investigate the magnetic transition temperature evolution under high pressure. Upon increasing the pressure from atmospheric pressure to 0.5 GPa, T_N (15.2 K) remains almost unchanged. Continuing to compress the sample results in T_N gradually decreasing to 14.8 K at 1.5 GPa. This may be due to pressure induced changes in the bond distance and bond angle of the O–C–O superexchange pathway. In addition, by using high pressure powder X-ray diffraction and Raman spectroscopy, we conducted in-depth research on the pressure dependence of the lattice parameters and Raman modes of [CH₃NH₃][Co(HCOO)₃]. The increase in pressure gives rise to a phase transition from the orthorhombic Pnma to a monoclinic phase at approximately 6.13 GPa. Our study indicates that high pressure can profoundly alter the crystal structure and magnetic properties of perovskite type MOF materials, which could inspire new endeavors in exploring novel phenomena in compressed metal–organic frameworks.