Magnetic phase diagram of an ErNi₂B₂C single crystal at low temperatures

We measured the magnetization M(T, H) of an ErNi₂B₂C single crystal with the applied magnetic field perpendicular and parallel to the c axis for temperatures below the superconducting transition temperature T_c. Only for the case of the magnetic field perpendicular to the c axis, the M(H) isotherm curves show several magnetic transitions even in the superconducting state. Such a behavior is similar to those of TbNi₂B₂C and HoNi₂B₂C compounds. However, unlike the behavior in TbNi₂B₂C, ferromagnetism coexists in ErNi₂B₂C at temperatures and fields well below T_c and H_c2- From the M (T, H) data, a magnetic phase diagram in the H - T plane was constructed for the magnetic field perpendicular to the c axis.