title: Magnetic properties of a novel quasi-2D Cu(II)-trimer system.
abstract: We present structural and magnetic data of a new Cu(2+)(S = 1/2)-containing magnetic trimer system 2b·3CuCl(2)·2H(2)O (b = betaine, C(5)H(11)NO(2)). The trimers form a quasi-2D quantum spin system with an unusual intra-layer exchange coupling topology, which, in principle, supports diagonal four-spin exchange. To describe the magnetic properties, a 2D effective interacting-trimer model has been developed including an intra-trimer coupling J and two inter-trimer couplings J(a) and J(b). The low-energy description and effective parameters are obtained from numerical calculations based on four coupled trimers (with periodic boundary conditions). Fits to the experimental data using this model yield the magnetic coupling constants J/k(B) = -15 K and J(a)/k(B) = J(b)/k(B) = -4 K. These parameters describe the susceptibility and magnetization data very well over the whole temperature and field range investigated. Moreover, the model calculations indicate that, for certain ranges of the ratio J(b)/J(a), which might be accessible by either chemical substitution and/or hydrostatic pressure, the low-energy properties of 2b·3CuCl(2)·2H(2)O will be dominated by non-trivial four-spin exchange processes.
authors.affiliation: Physikalisches Institut, Universität Frankfurt, SFB/TRR-49, D-60438 Frankfurt, Germany.
authors.forename: Katarina
authors.initials: K
authors.lastname: Remović-Langer
authors.forename: Eiken
authors.initials: E
authors.lastname: Haussühl
authors.forename: Leonore
authors.initials: L
authors.lastname: Wiehl
authors.forename: Bernd
authors.initials: B
authors.lastname: Wolf
authors.forename: Francesca
authors.initials: F
authors.lastname: Sauli
authors.forename: Nils
authors.initials: N
authors.lastname: Hasselmann
authors.forename: Peter
authors.initials: P
authors.lastname: Kopietz
authors.forename: Michael
authors.initials: M
authors.lastname: Lang