The POLI-instrument is dedicated to investigation of complex magnetic structures in single crystal samples using neutron spin polarisation. 3D polarisation analysis also known as spherical neutron polarimetry (SNP) using third generation zero-field polarimeter Cryopad is the implemented method.

Classical polarised neutron diffraction (PND) also known as flipping-ratio method will be implemented on POLI later. Neutron beam polarisation P can be treated as a classical vector. Zero-field SNP permits to measure all the components of the scattered polarisation vector. Determining the relationship between the directions of incident and scattered polarisations gives access to the 16 independent correlation functions involved in the most general nuclear and magnetic scattering process. Generally this leads to the termination of the direction of the magnetic interactions vectors of magnetic structures. For the structures in which nuclear and magnetic reflections are located in the same place in reciprocal space SNP leads to the determination of the amplitude of the magnetic interaction vectors, and hence to the magnetisation distribution.

Examples of the applications: precise verifying of complex commensurate and incommensurate magnetic structures, determination of anti-ferromagnetic form factors, studies of magnetic or magneto-electric domains (chirality).