Heat capacity uncovers physics of a frustrated spin tube

We report on refined experimental results concerning the low-temperature specific heat of the frustrated spin tube material [(CuCl2tachH)3Cl]Cl2. This substance turns out to be an unusually perfect spin tube system which allows to study the physics of quasi-one dimensional antiferromagnetic structures in rather general terms. An analysis of the specific heat data demonstrates that at low enough temperatures the system exhibits a Tomonaga-Luttinger liquid behavior corresponding to an effective spin-3/2 antiferromagnetic Heisenberg chain with short-range exchange interactions. On the other hand, at somewhat elevated temperatures the composite spin structure of the chain is revealed through a Schottky-type peak in the specific heat located around 2 K. We argue that the dominating contribution to the peak originates from gapped magnon-type excitations related to the internal degrees of freedom of the rung spins.Comment: 4+ pages, 6 figure

Linear, Trinuclear Cobalt Complexes with o-Phenylene-bis-Silylamido Ligands

Transamination of [Co{N(SiMe3)2}2]2 with C6H4(NHSiiPr3)2 gave the centrosymmetric trinuclear [{CoterN(SiMe3)2(μ-η-[o-C6H4(κNSiiPr3)2])}2Coint] ( 1 ) (Coter, Coint=terminal, internal Co, respectively), with 3-coordinate Coter, and Coint “sandwiched” between the o-phenylenes of the two ligands; experimental and computational data support CoII centres and ditopic o-amido-imino-cyclohexen-allyl ligands; magnetic studies reveal intermetallic ferromagnetic interactions and single-molecule magnet (SMM) character. One-electron reduction of 1 yielded the salt [K(18-crown-6)(THF)2][{CoterN(SiMe3)2(μ-η-[o-C6H4(κNSiiPr3)2])}2Coint] ( 4 ) with the anion isostructural to 1 . The centrosymmetric Fe complex [{FeterN(SiMe3)2(μ-η-[o-C6H4(κNSiiPr3)2])}2Feint] ( 5 ), analogous to 1 , was also obtained

Temperature effects on multi-particle scattering in a gapped quantum magnet

We report measurements of the temperature effects on the dimerized antiferromagnetic chain material, copper nitrate Cu(NO3)(2) (.) 2.5D(2)O. Using inelastic neutron scattering we have measured the temperature dependence of the one- and two-magnon excitation spectra as well as the temperature induced one-magnon intra-band scattering in a single crystal. Comparison is made with numerical evaluations of thermal averages based on the calculation for a chain of 16 spins. (c) 2006 Elsevier B.V. All rights reserved.</p