The nature of magnetic order in YBa2(Cu0.9Fe0.1)3O7.2: A neutron polarisation analysis study

Abstract Neutron polarisation analysis techniques have been used to extract the magnetic contributions to the total neutron scattering cross sections of a well characterized superconducting sample of YBa 2 (Cu 0.9 Fe 0.1 ) 3 O 7.2 . Paramagnetic-like scattering is seen between 1.5K and 300K. However there is no evidence at low temperature of either the long or short range magnetic order suggested by previous Mossbauer spectroscopy measurements. While susceptibility measurements indicate the Fe ions mainly adopt a high spin d 5 Fe 3+ configuration, the polarisation analysis measurements are consistent with an Fe spin closer to 3 2 . The discrepancy is attributed to spin fluctuations.