Magnetocaloric properties of V6 molecular magnet

Abstract

The paper presents a theoretical study of magnetocaloric properties of polyoxovanadate molecular magnet V6 containing 6 vanadium ions carrying quantum spins S = 1/2. The characteristic property of such structure is the presence of two weakly interacting spin triangles with all-antiferromagnetic couplings. The properties of the system are described using the exact numerical diagonalization approach applied to the quantum Heisenberg model and utilizing a field ensemble formalism. The dependence of the magnetic entropy and magnetic specific heat on the temperature and external magnetic field is calculated and extensively discussed. The magnetocaloric properties are quantified by isothermal entropy change and entropy derivative over the magnetic field. An interesting behaviour of isothermal entropy change is found, with high degree of tunability of the magnetocaloric effect with the initial and final magnetic field values.

Magnetocaloric Effect in Cu5-NIPA Molecular Magnet: A Theoretical Study

“…Between the field of 0 and 27.17 T, the most interesting gap ∆ 1 is a linearly increasing function of the field. It can be also seen that the second gap is usually significantly higher than the first gap (suggesting that the thermodynamics of the system in question can be Schottky model-like [38,51] and that the second excited state is usually well separated from the first excited state).…”

“…cube [45], a cuboctahedron [46], an edge-sharing tetrahedron [47], a hexagon [48], or a finite chain [49] clusters. Exact studies of Heisenberg model for particular molecular systems can also be found in the literature, e.g., a butterfly-shaped structure with higher spin [50] or our previous study concerning a structure with two interacting triangles [51]. The calculations become more even more demanding when structures involving high number of spins, especially S > 1/2, are modeled.…”

Effect of Single-Ion Anisotropy on Magnetocaloric Properties of Frustrated Spin-s Ising Nanoclusters

“…The experiment revealed isentropes with a rich structure, which were very well reproduced theoretically by considering a simple Heisenberg spin Hamiltonian with only exchange [17] or including also intramolecular dipolar interactions [18]. The observed isentropes were concluded to be a direct manifestation of the trigonal antiferromagnetic net structure, which triggered further experimental [19,20] and theoretical [21][22][23][24][25][26][27][28][29][30][31] studies of mainly frustration-enhanced MCE in finite systems of various shapes and topologies. They included geometrically frustrated Ising spin clusters with shapes of regular polyhedra [21,22] or triangular geometry [23][24][25][26][27].…”

Low-Temperature Magnetocaloric Properties of V12 Polyoxovanadate Molecular Magnet: A Theoretical Study

“…It can be highlighted that polyoxovanadate structures offer various cluster geometries as a platform for spin-1/2 magnetic systems, which leads to a variety of magnetocaloric properties. In this context, the triangle-based structure of V6 studied previously by us can be mentioned [ 51 ], which shows a ground state degeneracy in the absence of the magnetic field and also two quantum level crossings (taking place at rather high magnetic fields as compared to the case of V12). In V6, the energy gap between the ground state and the first excited state first rises linearly and then decreases linearly with the magnetic field.…”

“…In addition, the Heisenberg clusters were also studied, such as regular polyhedra [ 48 ], cuboctahedron [ 49 ], or cupolae [ 50 ]. In that context, we can also mention our recent works concerning particular molecular magnets, such as V6 polyoxovanadate [ 51 ] or Cu-based hourglass-shaped cluster [ 52 ], both based on triangular units.…”