Spin-1/2 XXZ Heisenberg cupolae: magnetization process and related enhanced magnetocaloric effect

Abstract

The magnetization curves and magnetocaloric effect during the adiabatic demagnetization of antiferromagnetic spin-1/2 XXZ Heisenberg clusters with the shape of Johnson's solids (triangular cupola, square cupola and pentagonal cupola) are investigated using the exact numerical diagonalization for different values of the exchange anisotropy ranging in between the Ising and fully isotropic limit. It is demonstrated that spin-1/2 XXZ Heisenberg cupolae display, in comparison with their Ising counterparts, at least one more magnetization plateau. The novel magnetization plateaux extends over a wider range of the magnetic fields with increasing of a quantum part of the XXZ exchange coupling at the expense of the original plateaux present in the limiting Ising case. It is shown that the spin-1/2 XXZ Heisenberg triangular and pentagonal cupolae exhibit an enhanced magnetocaloric effect in the vicinity of zero magnetic field, which makes these magnetic systems promising refrigerants for cooling down to ultra-low zero temperatures.

Theoretical analysis of magnetic properties and the magnetocaloric effect using the Blume-Capel model

“…Research on the properties of MCE and its applications has been growing both in the theoretical research [5][6][7][8][9][10][11][12] and in the experimental research [13][14][15][16][17][18][19]. From a theoretical point of view, statistical mechanics models are effective tools in the study of the thermodynamic and magnetic properties of materials.…”

Insights into Nature of Magnetization Plateaus of a Nickel Complex [Ni4(μ-CO3)2(aetpy)8](ClO4)4 from a Spin-1 Heisenberg Diamond Cluster

“…It should be pointed out, however, that the underlying mechanism for formation of intermediate magnetization plateau does not necessarily need to be of a purely 'quantum' origin, but it may sometimes have 'classical' character. The 'classical' plateau is a simple adiabatic continuation of a commensurate classical spin state realized in the Ising limit that is of course being subject to a quantum reduction of the local magnetization caused by quantum fluctuations, while the purely 'quantum' plateau relates to a massive quantum spin state with an energy gap that does not have any classical counterpart [24][25][26][27][28] .…”