CECOAL4 - AN INCOMMENSURATE ANTIFERROMAGNET

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 La2Ce1-xCoAl4 for x = 0.1 and 0.2 and CeCo1-yTyAl4 for T = Ni, Cu, and Pd. The crystal structure changes to YNiAl4-type even at low values of y (y approximate to 0.1 and T = Ni and Pd). We find that TN decreases when La or Cu is substituted for Ce and Co, respectively. The sharp increase in the resistivity near TN in CeCoAl4 is almost smeared out in these pseudoternaries.