Coupling of lattice and spin degrees of freedom in GdB6

Abstract A detailed X-ray scattering study of the phase transitions in GdB 6 has been performed. For photon energies away from resonance, peaks are observed with two distinct wave vectors of q 1 =(0 0 1 2 ) and q 2 =( 1 2 1 2 0) at low temperatures. These are shown to arise from distortions of the lattice, although an earlier study had attributed them to competing magnetic-order parameters [J. Appl. Phys. 63 (1998) 3580]. With the photon energy tuned to the Gd L 2 edge, a third set of peaks with q 3 =( 1 4 1 4 1 2 ) was discovered. This is shown to be the true magnetic-order parameter. Our results reveal a surprisingly rich interaction between the lattice and spin degrees of freedom in this compound.