Magnetization and magnetic phase diagrams of a spin-1/2 ferrimagnetic diamond chain at low temperature

• Published in: Chinese physics B 2021-05, Vol.30 (5), p.57503-719
• Main Authors: Cheng, Tai-Min, Li, Mei-Lin, Cheng, Zhi-Rui, Yu, Guo-Liang, Sun, Shu-Sheng, Ge, Chong-Yuan, Zhang, Xin-Xin
• Format: Article
• Language: English
• ISSN: 1674-1056
• DOI: 10.1088/1674-1056/abd768

We used the Jordan–Wigner transform and the invariant eigenoperator method to study the magnetic phase diagram and the magnetization curve of the spin-1/2 alternating ferrimagnetic diamond chain in an external magnetic field at finite temperature. The magnetization versus external magnetic field curve exhibits a 1/3 magnetization plateau at absolute zero and finite temperatures, and the width of the 1/3 magnetization plateau was modulated by tuning the temperature and the exchange interactions. Three critical magnetic field intensities H CB , H CE and H CS were obtained, in which the H CB and H CE correspond to the appearance and disappearance of the 1/3 magnetization plateau, respectively, and the higher H CS correspond to the appearance of fully polarized magnetization plateau of the system. The energies of elementary excitation ℏ ω σ , k ( σ = 1, 2, 3) present the extrema of zero at the three critical magnetic fields at 0 K, i.e., [ ℏ ω 3, k ( H CB )] min = 0, [ ℏ ω 2, k ( H CE )] max = 0 and [ ℏ ω 2, k ( H CS )] min = 0, and the magnetic phase diagram of magnetic field versus different exchange interactions at 0 K was established by the above relationships. According to the relationships between the system’s magnetization curve at finite temperatures and the critical magnetic field intensities, the magnetic field-temperature phase diagram was drawn. It was observed that if the magnetic phase diagram shows a three-phase critical point, which is intersected by the ferrimagnetic phase, the ferrimagnetic plateau phase, and the Luttinger liquid phase, the disappearance of the 1/3 magnetization plateau would inevitably occur. However, the 1/3 magnetization plateau would not disappear without the three-phase critical point. The appearance of the 1/3 magnetization plateau in the low temperature region is the macroscopic manifestations of quantum effect.