Determination of the Field Induce Magnetic Structure of Erbium Tetraboride

We propose to extend our investigations of the field induced behaviour of ErB4 on WISH. ErB4 is a rare realisation of the Shastry-Sutherland model, a frustrated system with an exact ground state solution. During our WISH experiment (03/2018), we followed the field evolution of the magnetic scattering and found two highly unusual effects. After exposure to B//c, i) the intensity of the magnetic peaks in zero field is significantly enhanced, ii) several magnetic reflections showed a pronounced "star" shape. It is crucial to investigate history dependence of the magnetic scattering in ErB4 to establish if a) the abnormal peak shape is induced on the 1/2 magnetisation plateau or the exposure to a saturation field (B>4 T) is required; b) the abnormal peak shape remains visible at higher temperatures; c) the enhanced zero-field intensity is influenced by the application of "negative" fields.