Crystal structure and magnetic properties of honeycomb-like lattice antiferromagnet $p$-BIP-V${}_{2}$

Crystal structure and magnetic properties of honeycomb-like lattice antiferromagnet $p$ -BIP-V $_{2}$

Hironori Yamaguchi, Shintaro Nagata, Masami Tada, Kenji Iwase, Toshio Ono, Sadafumi Nishihara, Yuko Hosokoshi, Tokuro Shimokawa, Hiroki Nakano, Hiroyuki Nojiri, Akira Matsuo, Koichi Kindo, and Takashi Kawakami

Phys. Rev. B 87, 125120 – Published 14 March 2013

Abstract

We successfully synthesized verdazyl biradical crystals of $p$ -BIP-V $_{2}$ [4,4 $^{'}$ -bis(1,5-diphenylverdazyl-3-yl)biphenyl]. Two types of intermolecular interactions are deduced from the spin-density distribution and molecular packing in the crystal, and these interactions are considered to result in the formation of a honeycomb lattice. The $ab$ $initio$ molecular orbital calculation also indicated such an exchange network of intermolecular interactions. The intramolecular interaction acts as a diagonal bridge across the honeycomb lattice to form a square lattice. We evaluated the intramolecular antiferromagnetic (AF) interaction $J_{1}$ to be about 8.8 K from an analysis of the magnetic susceptibility of isolated $p$ -BIP-V $_{2}$ molecules in terms of an isolated $S$ $=$ 1/2 AF dimer. We analyzed the magnetic susceptibility of the crystals using the quantum Monte Carlo method. Consequently, two types of intermolecular AF interactions, $J_{2}$ and $J_{3}$ , were found to be almost comparable and about 4.5 times larger than the intramolecular interaction $J_{1}$ . Thus, we confirmed that $p$ -BIP-V $_{2}$ has a slightly distorted $S = 1 / 2$ honeycomb-like lattice.