Magnetization processes and existence of reentrant phase transitions in coupled spin-electron model on doubly decorated planar lattices

Abstract

An alternative model for a description of magnetization processes in coupled 2D spin-electron systems has been introduced and rigorously examined using the generalized decoration-iteration transformation and the corner transfer matrix renormalization group method. The model consists of localized Ising spins placed on nodal lattice sites and mobile electrons delocalized over the pairs of decorating sites. It takes into account a hopping term for mobile electrons, the Ising coupling between mobile electrons and localized spins as well as the Zeeman term acting on both types of particles. The ground-state and finite-temperature phase diagrams were established and comprehensively analyzed. It was found that the ground-state phase diagrams are very rich depending on the electron hopping and applied magnetic field. The diversity of magnetization curves can be related to intermediate magnetization plateaus, which may be continuously tuned through the density of mobile electrons. In addition, the existence of several types of reentrant phase transitions driven either by temperature or magnetic field was proven.

Enhanced magnetoelectric effect of exactly solved spin-electron model on a doubly decorated square lattice in vicinity of a continuous phase transition

“…1). It is noteworthy that magnetic properties of the coupled spin-electron model on a doubly decorated square lattice have been comprehensively investigated in absence of the external electric field by assuming a quarter filling [12], a half filling [13,14] or a fractional filling [15][16][17][18] of the atomic orbitals of the decorating sites. The main focus of the present work will be therefore an influence of the external electric field upon magnetic properties of this correlated spin-electron model, which has not been dealt with previously.…”

“…However, these rigorous studies cannot bring insight, because of their low-dimensionality, into the magnetoelectric response in a close vicinity of temperature-driven phase transitions. The main goal of the present work is therefore to fill in this gap when considering a coupled spin-electron model on a doubly deco-rated square lattice, which exhibits a nontrivial criticality at finite temperatures notwithstanding of it exact solvability [12][13][14][15][16][17][18]. To achieve this goal, we will extend a coupled spin-electron model on a doubly decorated square lattice introduced in Refs.…”

Insights into Magnetic Properties of a Mixed Spin-Electron Model on Decorated Planar Lattices Composed of Half-filled Trigonal Bipyramids

“…In the specific case, where the quantum-mechanical hopping of mobile electrons is restricted to finite clusters coupled indirectly through the localized Ising spins, one may adapt the well-known concept of generalized mapping transformations [8][9][10][11] and thus obtain a relevant exact solution of the proposed model. To date, this approach has been successfully applied to various one-(1D) [12][13][14][15][16][17][18][19][20][21][22][23][24] and two-dimensional (2D) [25][26][27][28][29][30][31][32] lattice structures. Despite of their relative simplicity, the investigated mixed spin-electron models have proven to be suitable to simulate many unconventional physical properties and unusual cooperative phenomena with a good qualitative coincidence of the magnetic behavior of real materials.…”

“…Despite of their relative simplicity, the investigated mixed spin-electron models have proven to be suitable to simulate many unconventional physical properties and unusual cooperative phenomena with a good qualitative coincidence of the magnetic behavior of real materials. We can mention, for example, the kinetically-driven frustration of the Ising sub-lattice, [13][14][15][16][17][18][19][22][23][24] the local chirality in the electron sub-lattice, [15][16][17][18]22) rational 12-15, 17, 18, 23, 24, 28) and doping-dependent 17,19) magnetization plateaus in magnetization curves, double-and also triple-peak temperature dependences of the specific heat, 12-15, 22, 23) temperature-induced reentrant phase transitions, [26][27][28]31) the bipartite fermionic entanglement between mobile electrons, 20,21,24) and, last but not least, also the enhanced magnetocaloric 16,18) or magnetoelec-tric 29,30,32) effects.…”

Comparative Study of a Critical Behavior of a Coupled Spin-Electron Model on a Doubly Decorated Square Lattice in the Canonical and Grand-Canonical Ensemble

“…5-17 therein). In the present work, we will examine a relatively simple doubly decorated spin-electron model on a square lattice (DDSEM), which was successfully used to elucidate the origin of some unconventional phenomena in coupled spin-electron systems like a doping-induce crossover from ferro-to antiferromagnetism [3,4], an enhanced magnetoelectric effect [5], metamagnetic transitions [6] or magnetic re-entrance [7]. Our main attention will be concentrated on the comparative study of a critical behavior in the canonical ensemble (CE) and grand-canonical one (GCE), with a motivation to examine if the choice of the statistical ensemble could have a significant impact on a critical temperature in the DDSEM, where the intrinsic features can be modified by an extrinsic factor like an electric field.…”