T violation   The discussion of why a nonzero EDM for the neutron violates P and T and thus CP is not strictly true for a spin particle the only axis of quantisation  and thus the only well defined direction  is proportional to its spin Hence we have to define the EDM d to be along that axis the term entering the Hamiltonian is dE which is Todd and Podd Acting with T reverses the neutrons spin and thus d acting with P reverses the direction of E  hence giving rise to the CP violation httparxivorgpdfv Im not convinced by the magnetic moment picture painted and I may well update the page after consulting with my more learned colleagues