title: Experimental Realization of a Quantum Pentagonal Lattice.
abstract: Geometric frustration, in which competing interactions give rise to degenerate ground states, potentially induces various exotic quantum phenomena in magnetic materials. Minimal models comprising triangular units, such as triangular and Kagome lattices, have been investigated for decades to realize novel quantum phases, such as quantum spin liquid. A pentagon is the second-minimal elementary unit for geometric frustration. The realization of such systems is expected to provide a distinct platform for studying frustrated magnetism. Here, we present a spin-1/2 quantum pentagonal lattice in the new organic radical crystal α-2,6-Cl2-V [=α-3-(2,6-dichlorophenyl)-1,5-diphenylverdazyl]. Its unique molecular arrangement allows the formation of a partially corner-shared pentagonal lattice (PCPL). We find a clear 1/3 magnetization plateau and an anomalous change in magnetization in the vicinity of the saturation field, which originate from frustrated interactions in the PCPL.
authors.affiliation: Department of Physical Science, Osaka Prefecture University, Osaka 599-8531, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Yamaguchi
authors.affiliation: Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Okubo
authors.affiliation: Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan.
authors.forename: Shunichiro
authors.initials: S
authors.lastname: Kittaka
authors.affiliation: Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan.
authors.forename: Toshiro
authors.initials: T
authors.lastname: Sakakibara
authors.affiliation: Department of Applied Physics, National Defense Academy, Kanagawa 239-8686, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Araki
authors.affiliation: Department of Physical Science, Osaka Prefecture University, Osaka 599-8531, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Iwase
authors.affiliation: Department of Physical Science, Osaka Prefecture University, Osaka 599-8531, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Amaya
authors.affiliation: Department of Physical Science, Osaka Prefecture University, Osaka 599-8531, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Ono
authors.affiliation: Department of Physical Science, Osaka Prefecture University, Osaka 599-8531, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Hosokoshi