Magnetic Grüneisen parameter and magnetocaloric properties of a coupled spin–electron double-tetrahedral chain

Abstract

Magnetocaloric effect in a double-tetrahedral chain, in which nodal lattice sites occupied by the localized Ising spins regularly alternate with three equivalent lattice sites available for mobile electrons, is exactly investigated by considering the one-third electron filling and the ferromagnetic Ising exchange interaction between the mobile electrons and their nearest Ising neighbours. The entropy and the magnetic Grüneisen parameter, which closely relate to the magnetocaloric effect, are exactly calculated in order to investigate the relation between the ground-state degeneracy and the cooling efficiency of the hybrid spin-electron system during the adiabatic demagnetization.

Magnetization plateau as a result of the uniform and gradual electron doping in a coupled spin-electron double-tetrahedral chain

“…The magnetic structure of this 1D lattice is experimentally realized in the copper-based polymeric chain Cu 3 Mo 2 O 9 [52][53][54][55]. As has been shown in our recent works [56][57][58][59], the mixed spin-electron system with the lattice topology of the double-tetrahedral chain represents an excellent prototype model, which allows the exact investigation of many interesting physical phenomena such as quantum non-chiral and/or uncommon chiral ground states, the rational magnetization plateau, the abnormally narrow and high low-temperature peak of the specific heat and very abrupt (almost discontinuous) thermal variations of the entropy and sublattice magnetization caused by a difference in ground-state degeneracies, as well as the enhanced magnetocaloric effect. The main purpose of this paper is to explore in detail an effect of the uniform and gradual electron doping on the ground-state properties of the model and the plateau creation in the magnetization process in order to provide a deeper insight into doping-dependent magnetization plateaux.…”

Hubbard pair cluster in the external fields. Studies of the polarization and susceptibility

“…At the same time, it has been noticed that the exact solutions to the model can be obtained for small clusters, consisting of several lattice sites [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84]. Intensive investigations of such systems have been carried out both from the point of view of static properties [48-50, 52, 58, 62, 64, 66-68, 71-73, 75-80, 82, 83, 85-88], as well as for dynamical description [54,59,61,70,81,84].…”

Hubbard pair cluster in the external fields. Studies of the chemical potential

“…The influence of temperature, Hubbard on-site Coulombic energy U and electron concentration on the chemical potential is investigated and illustrated in figures. In particular, a discontinuous behaviour of the chemical potential (or electron concentration) in the ground state is discussed.Quantum Monte Carlo (QMC) methods [18,42] and Dynamical Cluster Approximation (DCA) [20] deserve particular attention.The possible extensions of the domain where the exact solutions can be found for the model include the zero-dimensional, cluster systems (see for example [22,23]) as well as clusters embedded in the environment of localized spins [24][25][26][27]. It is worthy to mention that the studies of such geometrically confined, cluster systems are important from the point of view of nanophysics and nanotechnology.…”