Calculation of Magnetic Properties and Ground State of Various Novel Organic Radical Magnets by Using ALPS
Owing to the wide diversity of chemical modifiers in organic materials, over one million organic molecules have been synthesized artificially so far. While mainly inorganic magnets have been focused in the research of magnetism, the aim of our research is to introduce a diversity of organic materials into the discipline. Our research has revealed that a stable radical called feldazyl radical can be utilized to suppress the undesirable properties that prevent the synthesis of organic magnets. Our findings thus accelerate synthesis of new organic magnetic materials drastically, leading to realization of various quantum spin models [1-4].
The quantum Monte Carlo method provided in ALPS is used to investigate quantum magnetic states quantitatively. Owing to the versatility of ALPS, any spin model can be defined using the XML language, and it can therefore be adapted to a wide variety of quantum spin models.
The new organic radical β-2,6-Cl2-V is expected to form a spin-½ antiferromagnetic chain of three different interactions with fourfold periodicity. We used ALPS to investigate its magnetic properties and the ground state . We have succeeded in explaining the magnetic properties quantitatively, including the quantized ½-magnetization plateau, as shown in Figure 1. Furthermore, based on the parameters obtained through this analysis, we applied the perturbation theory to discuss the ground state. It is found that in the low magnetic field region, the spin-½ bond-alternating antiferromagnetic chain is realized, while in the high magnetic field region, the ferromagnetic Ising spin chain is formed effectively (Fig. 2). The combination of the rich diversity of organic radicals and the versatility of ALPS can bring further understanding of new quantum spin models and discoveries of new exotic spin states.
Figure 1: Magnetization curves of β-2,6-Cl2-V at 1.3K. The lower inset shows those at 0.15, 0.30, and 0.60 K in the low-field region; the upper inset shows their field derivative.
Figure 2: Effective magnetic states of β-2,6-Cl2-V in (a) low magnetic field and (b) high magnetic field regions.