Magneto-elastic Coupling Across the First-order Transition in the Distorted Kagome Lattice Antiferromagnet DyRuAl

Structural changes through the first-order paramagnetic-antiferromagnetic phase transition of DyRuAl at 7 K have been studied by means of X-ray diffraction and thermal expansion measurements. The compound crystallizes in a hexagonal crystal structure of GdRuAl type (6/ space group), and no structural phase transition has been found in the temperature interval between 2.5 and 300 K. Nevertheless, due to the spin-lattice coupling the crystal volume undergoes a small orthorhombic distortion of the order of 2×10 as the compound enters the antiferromagnetic state. We propose that the first-order phase transition is not driven by the structural changes but rather by the exchange interactions present in the system.