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 a ntiferromagnetically 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, th e 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 inc reasing magnetic field. At 16 T, we found a value of T-N 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 ferromagne tic order. Along the c-axis, a drastic change in the specific heat occurs a t a field between 7-8 T. At 7 T, the value of T-N is about 9 K. At fields h igher than 8 T, the specific heat is evidently characterised by a transitio n from paramagnetism to ferromagnetic order. The critical values of the mag netic field above which ferromagnetic order is formed at low temperature tu rn out to be consistent with the measurements of the magnetisation curves a t 4.2 K. (C) 1998 Elsevier Science S.A. All rights reserved.