Study of the specific heat of a CeCoAl4 single crystal in high magnetic fields

The specific heat of a CeCoAl4 single crystal has been studied in magnetic fields up to 17.5 T. In zero field, this compound has been found to order antiferromagnetically below the Neel temperature of about 13.5 K. The effect of the magnetic field is different when it is applied along the different crystallographic axes. Along the a-axis, with increasing magnetic field, the Neel temperature slightly decreases and reaches a value of 12.7 K at 17.5 T. Along the b-axis, the Neel temperature decreases more strongly with increasing magnetic field. At 16 T, we found a value of TN of about 6.9 K. At 17.5 T, along the b-axis, we observed a rather broad peak in the specific heat which is associated with a transition from paramagnetism to ferromagnetic order. Along the c-axis, a drastic change in the specific heat occurs at a field between 7-8 T. At 7 T, the value of TN is about 9 K. At fields higher than 8 T, the specific heat is evidently characterised by a transition from paramagnetism to ferromagnetic order. The critical values of the magnetic field above which ferromagnetic order is formed at low temperature turn out to be consistent with the measurements of the magnetisation curves at 4.2 K. (orig.)