Magnetocaloric properties of frustrated tetrahedra-based spin nanoclusters

Abstract

Magnetization, entropy and magnetocaloric properties of various geometrically frustrated tetrahedra-based Ising antiferromagnetic nanoclusters with corner-, edge-, and face-sharing topologies are studied by exact enumeration. It is found that the studied properties strongly depend on the nanocluster topology and can be very different from those of a single tetrahedron as well as the pyrochlore lattice formed by an infinite number of corner-sharing tetrahedra. From the magnetocaloric point of view an important difference from the latter two systems is the absence of the ground-state zero-magnetization plateau in most of the studied structures, which at low temperatures facilitates emergence of a giant magnetocaloric effect in a vanishing magnetic field in the adiabatic demagnetization process. Magnetic systems with such properties might be suitable candidates for technological application as efficient refrigerators to ultra-low temperatures.

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

“…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]. It turns out that magnetocaloric properties are highly sensitive to the cluster geometry.…”

“…It turns out that magnetocaloric properties are highly sensitive to the cluster geometry. In particular, for low-temperature cooling spin clusters which lack zero-magnetization plateaus in an applied magnetic field at zero temperature, such as the octahedron and dodecahedron from the regular polyhedra [21] and most of the studied clusters composed of triangular plaquettes [25][26][27], were identified as promising candidates since they exhibited a giant magnetocaloric effect in the process of adiabatic demagnetization.…”

“…Nevertheless, besides the shape and topology there are other properties, such as spin, anisotropy (both exchange and single-ion), higher-order interactions, surface effects, etc., that can affect the spin system properties [32][33][34][35] including their magnetocaloric behavior [36][37][38][39]. In the present paper, we focus on two types of the geometrically frustrated triangle-based Ising nanoclusters with antiferromagnetic interaction that have shown favorable low-temperature MCE for s = 1/2 [25,27] and generalize them by considering a higher spin s ≥ 1 and inclusion of the single-ion anisotropy. In particular, we study a simple triangular (T) cluster [25] and a cluster composed of two corner-sharing (2CS) tetrahedra [27].…”

“…In the present paper, we focus on two types of the geometrically frustrated triangle-based Ising nanoclusters with antiferromagnetic interaction that have shown favorable low-temperature MCE for s = 1/2 [25,27] and generalize them by considering a higher spin s ≥ 1 and inclusion of the single-ion anisotropy. In particular, we study a simple triangular (T) cluster [25] and a cluster composed of two corner-sharing (2CS) tetrahedra [27]. We demonstrate that their magnetocaloric properties strongly depend on both the spin as well as the sign and magnitude of the single-ion anisotropy and identify some particular arrangements that can lead to a giant MCE in a small or even vanishing magnetic field in the adiabatic demagnetization process.…”

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

“…The theoretical works concerning the exact characterization of magnetocaloric properties of the model magnetic clusters that are composed of spins involve, for example, various Ising systems, to mention regular polyhedra [ 42 , 43 ], tetrahedra [ 44 ] or triangle-based clusters [ 45 , 46 , 47 ]. In addition, the Heisenberg clusters were also studied, such as regular polyhedra [ 48 ], cuboctahedron [ 49 ], or cupolae [ 50 ].…”