The proposal develops recent observations on spin-lattice coupling in incommensurate materials (objective - measure influence of applied field on evolution of structural modulation wavevectors through the spin freezing transition) and the proposed multiferroic Bi2FeCrO6 (objective - evaluate low temperature magnetic structure and spin-lattice coupling through the magnetic ordering transition). New materials synthesised under high pressure will be refined to evaluate cation ordering. Small sample sizes and the need for both high count rate and resolution make GEM essential for these studies.