Polarisation analysis for the determination of magnetic structures in highmagnetic fields

We have upgraded an existing two axis spectrometer for polarisation analysi s experiments using supermirror polarisers. The instrument is fully compati ble with a complex sample surrounding, including high magnetic fields up to 7T. The primary use of this spectrometer is the determination of spin dire ctions. The polarisation analysis technique is well suited for problems whe re only a few magnetic reflections can be investigated for the determinatio n of a structure as it provides selection rules, in addition, to the well-k nown dipolar selection rule. The instrument has been applied for the invest igation of the field dependent phase diagram on K2IrCl6. There a multiple q structure is identified in high field which presumably can only be explain ed by the presence of biquadratic exchange interactions. (C) 2001 Elsevier Science B.V. All rights reserved.