Exploring Spin-Phonon Coupling in Magnetic 2D Metal-Organic Frameworks.

Layered magnetic metal-organic frameworks (MOFs) are an emerging class of materials that can combine the advantages of both MOFs and 2D magnetic crystals. The recent discovery of large coercivity and long-range magnetic ordering up to 515 K in a layered MOF of general formula MCl(pyz) (M = transition metal, pyz = pyrazine) offers an exciting versatile platform to achieve high-T magnetism at the 2D limit. In this work, we investigate the exfoliation feasibility down to the monolayer of VCl(pyz) and CrCl(pyz) by means of first-principles calculations. We explore their structural, electronic, magnetic and vibrational properties, as well as the effect of halide substitution. Then, we provide a full analysis of the spin-phonon coupling (SPC) in both 2D derivatives. Our calculations reveal a low SPC and thermal evolution of the magnetic exchange interactions and single-ion anisotropy mainly governed by low-frequency phonon modes. Finally, we provide chemical insights to improve the performance of these magnetic 2D MOFs based on the effective manipulation of the phonon modes that can present a major impact on their magnetic properties.