title: Magneto-structural correlations in a 1,3,2-dithiazolyl radical crystal, BBDTAGaBr4: structure and magnetic properties of its three polymorphs.
abstract: We investigate the preparation, crystal growth, crystal structure, and magnetic properties of the three polymorphs (alpha, beta, and gamma) of an organic magnet, BBDTA(= benzo[1,2-d:4,5-d'] bis[1,3,2]dithiazole) x GaBr(4), which is an S-1/2 system. In the alpha phase, BBDTA(+) units form a square-planar lattice, and show canted antiferromagnetism with a magnetic coupling constant J/k(B) of -18 K and a canting angle of 0.15 degrees below 15.5 K. The beta phase is composed of a ferromagnetic regular chain with a J/k(B) value of +4.5 K and a strong antiferromagnetic chain with J/k(B) = -99 K, and shows ferromagnetic ordering in spins of purely the ferromagnetic chain below 0.4 K. The gamma phase is isostructural with gamma-BBDTA x GaCl(4), which is an organic ferromagnet below 7.0 K, and possesses antiferromagnetic interactions of J/k(B) = -60 K between BBDTA(+) cations, and shows no magnetic ordering until 2 K. The magnetic properties of these phases are quite sensitive to the molecular alignment in the crystals.
authors.affiliation: Department of Chemistry, Tokyo Metropolitan University, Minami-osawa 1-1, Hashioji 192-0397, Japan. fujitaw@tmu.ac.jp
authors.forename: Wataru
authors.initials: W
authors.lastname: Fujita
authors.forename: Koichi
authors.initials: K
authors.lastname: Kikuchi