title: S=1/2 one-dimensional random-exchange ferromagnetic zigzag ladder, which exhibits competing interactions in a critical regime.
abstract: The synthesis, crystal structure, and magnetic properties (from a combined experimental and First-Principles Bottom-Up theoretical study) of the new compound catena-dichloro(2-Cl-3Mpy)copper(II), 1, [2-Cl-3Mpy=2-chloro-3-methylpyridine] are described and rationalized. Crystals of 1 present well isolated magnetic 1D chains (no 3D order was experimentally observed down to 1.8 K) and magnetic frustration stemming from competing ferromagnetic nearest-neighbor (J(NN)) interactions and antiferromagnetic next-nearest neighbor (J(NNN)) interactions, in which α=J(NNN)/J(NN) <-0.25. These magnetic interactions give rise to a unique magnetic topology: a two-leg zigzag ladder composed of edge-sharing up-down triangles with antiferromagnetic interactions along the rails and ferromagnetic interactions along the zigzag chain that connects the rails. Crystals of 1 also present a random distribution of the 2-Cl-3Mpy groups, which are arranged in two different orientations, each with a 50 % occupancy. This translates into a random static structural disorder within each chain by virtue of which the value of the J(NN) magnetic interactions can randomly take one of the following three values: 53, 36, and 16 cm(-1). The structural disorder does not affect the J(NNN) value, which in all cases is approximately -9 cm(-1). A proper statistical treatment of this disorder provides a computed magnetic susceptibility curve that reproduces the main features of the experimental data.
authors.affiliation: Carlson School of Chemistry and Biochemistry, Clark Universitym, 950 Main St. Worcester, MA 01610 (USA), Fax: (+1) 508-793-7117.
authors.forename: Susan N
authors.initials: SN
authors.lastname: Herringer
authors.forename: Mercè
authors.initials: M
authors.lastname: Deumal
authors.forename: Jordi
authors.initials: J
authors.lastname: Ribas-Arino
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Novoa
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Landee
authors.forename: Jan L
authors.initials: JL
authors.lastname: Wikaira
authors.forename: Mark M
authors.initials: MM
authors.lastname: Turnbull
keywords: coordination polymers; density functional calculations; exchange interactions; random structural disorder; spin frustration