Modeling molecular magnets with large exchange and on-site anisotropies

Sumit Haldar (1) , Rajamani Raghunathan (2) , J.-P. Sutter (3) , S. Ramasesha (1)

1 Solid State and Structural Chemistry Unit, Indian Institute of Science
2 UGC-DAE Consortium for Scientific Research
3 LCC - Laboratoire de chimie de coordination

Spins in molecular magnets can experience both anisotropic exchange interactions and on-site magnetic anisotropy. In this paper, we study the effect of exchange anisotropy on the molecular magnetic anisotropy both with and without on-site anisotropy. When both the anisotropies are small, we find that the axial anisotropy parameter DM in the effective spin Hamiltonian is the sum of the individual contributions due to exchange and on-site anisotropies. We find that even for axial anisotropy of about 15%, the low-energy spectrum does not correspond to a single-parent spin manifold but has intruder states arising from other parent spins. In this case, the low-energy spectrum cannot be described by multiplet states arising from a single approximate total spin state. We study the magnetic susceptibility, specific heat as a function of temperature, and magnetization as a function of applied field to characterize the system in this limit. We find that there is synergy between the two anisotropies, particularly for large systems with higher site spins.

Domaines: Chimie de coordination

Sumit Haldar, Rajamani Raghunathan, J.-P. Sutter, S. Ramasesha. Modeling molecular magnets with large exchange and on-site anisotropies. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2018, 98 (21), pp.214409/1-10. ⟨10.1103/PhysRevB.98.214409⟩. ⟨hal-01962515⟩