CeCoAl₄: an incommensurate antiferromagnet

Abstract

The orthorhombic compound CeCoAl₄ orders antiferromagnetically at a relatively high Neel temperature T_N of 13 K. The resistivity of CeCoAl₄ shows a sharp increase near the magnetic transition before decreasing with temperature below 12 K. We believe that such behavior is due to the energy gaps induced by the incommensurate antiferromagnetic order. We have also studied the solid solutions La_xCe_1-xCoAl₄ for x=0.1 and 0.2 and CeCo_1-yT_yAl₄ for T=Ni, Cu, and Pd. The crystal structure changes to YNiAl₄-type even at low values of y (y~=0.1 and T=Ni and Pd). We find that T_N decreases when La or Cu is substituted for Ce and Co, respectively. The sharp increase in the resistivity near T_N in CeCoAl₄ is almost smeared out in these pseudoternaries.