Completing the phase diagram of a 2D molecular antiferromagnet

Low-dimensional quantum magnetism continues to be of great theoretical and experimental interest as reduced dimensionality supports strong quantum fluctuations which can result in novel excitations and critical behaviour. Here we propose to complete an investigation of the phase diagram of a series of molecular 2D quantum Heisenberg antiferromagnets with random exchange strengths. This is a project started at PSI by Dr Fan Xiao, where materials from the series (QuinH)2Cu(Br(1-x)Clx)4.2H2O with x < 0.5 were successfully measured. Our recent measurement at ISIS has shown magnetic order in the x=1 member of the series, but the nature of the signal brings into question whether the system is ever quantum disordered. We now seek to measure two final compounds with high Cl concentrations in order to complete our investigation of the phase diagram of the system.