Abstract
Advances in quantum computing technology have been made in recent years due to the evolution of spin clusters. Recent studies have tended towards spin cluster subgeometries to understand more complex structures better. These molecular magnets provide a multitude of phenomena via exchange interactions that allow for advancements in spintronics and other magnetic system applications due to the possibility of increasing speed, data storage, memory, and stability of quantum computing systems. Using the Heisenberg spin–spin exchange Hamiltonian and exact diagonalization, we examine the evolution of quantum energy levels and thermodynamic properties for various spin configurations and exchange interactions. The XXYY quantum spin tetramer considered in this study consists of two coupled dimers with exchange interactions α1J and α1′J and a dimer–dimer exchange interaction α2J. By varying spin values and interaction strengths, we determine the exact energy eigenstates that are used to determine closed-form analytic solutions for the heat capacity and magnetic susceptibility of the system and further analyze the evolution of the properties of the system based on the parameter values chosen. Furthermore, this study shows that the Schottky anomaly shifts towards zero as the ground-state of the system approaches a quantum phase transition between spin states. Additionally, we investigate the development of phase transitions produced by the convergence of the Schottky anomaly with both variable exchange interactions and external magnetic field.
Highlights
In the journey towards the advancement of quantum computing, the tunability of molecular magnets has led to a better understanding of quantum tunneling applications, quantum dots, and anisotropic effects in materials in both theoretical and experimental research [1,2,3,4,5,6,7,8]
This study shows that the Schottky anomaly shifts towards zero as the ground-state of the system approaches a quantum phase transition between spin states
The focus of this paper is to provide a complete understanding of the quantum spin tetramer and its bulk thermodynamic properties
Summary
In the journey towards the advancement of quantum computing, the tunability of molecular magnets has led to a better understanding of quantum tunneling applications, quantum dots, and anisotropic effects in materials in both theoretical and experimental research [1,2,3,4,5,6,7,8]. The systems can be manipulated to speeds in the THz range for high-density storage and ultra-fast switching due to the typically small energy shifts between states [30] These features offer an advantage over ferromagnetic (FM) spin clusters since FM systems tend to have larger total magnetic moments and are likely to be unstable in environments with external magnetic fields [1,31]. The tetramer configurations consist of three different exchange interactions that can be changed independently (antiferromagnetic and ferromagnetic), symmetric and asymmetric systems (XXXX and XXYY spin configuration, respectively) are examined for bulk properties excluding magnetic susceptibility, one mixed-valence case (XXYY spin configuration) is covered to show how magnetic susceptibility evolves with varying exchange interaction strengths in comparison to ground-state/quantum phase transitions and heat capacity, and the systems are explored and compared with and without a varying magnetic field. A low-temperature restriction (from 0 to 1 K) is used to approach the study in the quantum regime
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