Magnetic behavior of the metal organic framework solid: [(CH3)2NH2][Co(HCOO)3]

TL;DR

This study investigates the magnetic phase transitions of [(CH3)2NH2]Co(HCOO)3], revealing an antiferromagnetic transition at 15 K, coexistence of single-ion magnetism, and a structural transition at 155 K with associated spin-state change.

Contribution

It provides detailed experimental insights into the magnetic and structural phase transitions in this specific metal-organic framework compound.

Findings

Antiferromagnetic transition at 15 K confirmed by magnetization and specific heat.

Coexistence of single-ion magnetism with antiferromagnetism observed.

Structural transition at 155 K linked to a Co2+ spin-state change.

Abstract

In this study we examine the phase transitions in single crystals of [(CH3)2NH2]Co(HCOO)3], using magnetization and specific heat measurements as a function of temperature and magnetic field. Magnetisation measurements indicate a transition at 15 K that is associated with an antiferromagnetic transition. The results of the isothermal magnetization versus magnetic field curves demonstrate the presence of a single-ion magnet phase, coexisting with antiferromagnetism. A peak in specific heat is seen at 15 K, corresponding to the magnetic transition. The enthalpy of the transition evaluated from the area under the specific heat peak decreases with the application of magnetic field of upto8 T. This is suggestive of long range antiferromagnetic magnetic order, giving way to single-ion magnetic behavior under external field. In experiments at high temperatures, corresponding to the well-known structural transition in this system, the specific heat measurements, shows a peak at ~155K, that is insensitive to applied magnetic field. The magnetisation in this temperature range, while it exhibits a paramagnetic behavior, shows a distinct jump that has been attributed to a spin-state transition of Co2+ associated with the structural transition.