title: Unconventional magnetic and thermodynamic properties of S=1/2 spin ladder with ferromagnetic legs.
abstract: We have succeeded in synthesizing single crystals of a new organic radical 3-Cl-4-F-V [3-(3-chloro-4-fluorophenyl)-1,5-diphenylverdazyl]. Through the ab initio molecular orbital calculation and the analysis of the magnetic properties, this compound was confirmed to be the first experimental realization of an S=1/2 spin-ladder system with ferromagnetic leg interactions. The field-temperature phase diagram indicated that the ground state is situated very close to the quantum critical point. Furthermore, we found an unexpected field-induced successive phase transition, which possibly originates from the interplay of low dimensionality and frustration.
authors.affiliation: Department of Physical Science, Osaka Prefecture University, Osaka 599-8531, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yamaguchi
authors.affiliation: Department of Physical Science, Osaka Prefecture University, Osaka 599-8531, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Iwase
authors.affiliation: Department of Physical Science, Osaka Prefecture University, Osaka 599-8531, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ono
authors.affiliation: Center for Collaborative Research and Technology Development, Kobe University, Kobe 657-8501, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Shimokawa
authors.affiliation: Graduate School of Material Science, University of Hyogo, Hyogo 678-1297, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Nakano
authors.affiliation: Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Shimura
authors.affiliation: Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Kase
authors.affiliation: Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kittaka
authors.affiliation: Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Sakakibara
authors.affiliation: Department of Chemistry, Osaka University, Osaka 560-0043, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kawakami
authors.affiliation: Department of Physical Science, Osaka Prefecture University, Osaka 599-8531, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Hosokoshi