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Abstract: Elastic neutron scattering experiments on the pressure-induced ferromagnetic superconductor have been carried out under pressures P up to 1.6GPa at temperatures T down to 60mK, to study the correlation between superconductivity and ferromagnetism. No change was observed in ferromagnetic Bragg peak intensities nor a line width at through the superconducting transition temperature under and 1.25GPa, suggesting that the ferromagnetism is not affected by the onset of superconductivity under these two pressures. [Copyright &y& Elsevier]

We have measured magnetization curves of the pressure-induced ferromagnetic superconductor UGe2 at temperatures down to 0.5 K under various pressures. The ferromagnetic hysteresis loop is smooth down to about 1 K, but on further decreasing temperature, the hysteresis suddenly changes into a staircase-like curve, and the jump occurs at regular interval of magnetic field. We ascribe this novel finding to the macroscopic quantum tunneling effect (MQT). An analysis based on MQT suggests tiny magnetic domain formation whose size is smaller than the superconducting coherence length. [Copyright &y& Elsevier]