Zero-field magnetic structure and metamagnetic phase transitions of the cobalt chain compound Li₂CoCl₄

Exploring the uncharacterized magnetic phases of Co2+ chain compounds is critical for finding new low-dimensional magnets hosting quantized excitations. We map the unexplored magnetic phases of the Co2+ chain compound Li2CoCl4. Magnetometry reveals magnetic ordering below 7 K with a metamagnetic transition near 16.5 kOe and a gradual transition to a field-aligned paramagnetic state above 31 kOe. Curie-Weiss fits to the high temperature susceptibility reveal a high-spin (spin-3/2) state for cobalt. Heat capacity data, though, give a magnetic entropy change of 5.46 J/mol, consistent with cobalt effective spin-1/2 systems. To characterize the zero-field antiferromagnetic ordering, we separately calculated the energy of proposed magnetic structures with density functional theory and collected 3.5 K neutron diffraction data, finding that Li2CoCl4 has ferromagnetic chains with antiferromagnetic interactions between them. Increasing field rotates these spin chains, producing the antiferromagnetic to intermediate to paramagnetic transition sequence.