Search for Anomalous Spin-Spin Interactions Using a Paramagnetic Salt with a DC SQUID

We use a paramagnetic salt TbF₃ with a DC SQUID to search for a possible anomalous spin-spin interaction of two rotating HoFe₃ polarized bodies with the TbF₃ paramagnetic salt. We set limits on the electron-electron spin interaction and the electron-nucleus spin interaction. In terms of a standard dipole-dipole form, the limits are (-2.1 ±3.5)×10^-14 for the anomalous spin-spin interaction of electrons in terms of the interaction strength between the magnetic moments of the electrons, and (-2.1±3.6)×10^-8 for the anomalous spin-spin interaction between the electron and the Ho-nucleus in terms of the interaction strength between the magnetic moments of the electron and the Ho-nucleus.