Splitting of the longitudinal Neel transition in erbium in a c-axis magnetic field

We have examined the magnetic phase diagram of single-crystal erbium in the temperature range between 60 K and 90 K and in applied magnetic fields along the c-axis up to 5.5 T using resistance versus temperature and magnetoresistance measurements. The H-T phase diagram for that region is presented. We have observed a splitting of the longitudinal Neel transition near 1.6 T. We have found a new phase with unknown structure in that portion of the phase diagram created by the splitting of the Neel transition. We have also found a multicritical point (P) at an applied field of 2.65 T and 71 K. A set of five magnetic phase lines appears to meet at this multicritical point. (author)