Magnetic phase diagram and crystal fields of superconducting ErNi2B2C

We have measured the specific heat cp in magnetic fields and the resistance of the antiferromagnetically ordered borocarbide superconductor ErNi2B2C. From our data we show that the superconductivity at 10.6 K coexists with antiferromagnetic order beginning at 5.8 K, and we determine the magnetic B-T phase diagram. The specific heat in zero field gives additional information about the crystalline electric field (CEF) splitting. We show that the low-temperature specific heat is dominated by several low-lying CEF doublets with the first excited level at about 10 K, while the splitting of the next two levels is about 50 to 100 K. (orig.)