Modification of Charge and Spin Textures by Light Chemical Substitution in Eu[Al_xGa_1-x]₄, x=0.9

In this talk, I will present the results of a resonant X-ray diffraction experiment elucidating both charge and magnetic textures in the intermetallic topological magnet Eu[Al_xGa_1-x]₄, x=0.9. We show that below ≈75K the system develops a CDW with propagation vector k_CDW=(0,0,0.18). The CDW order parameter grows continuously on cooling until ≈15K, when a sudden decrease in the CDW amplitude occurs. Magnetic satellites of the (0,0,8) Bragg reflection, (k₁ = [+/-0.2, 0, 0], k₂ = [0, +/-0.2, 0]), were studied at the Tb L_III-edge; the pairs correspond to two domains with k_i parallel to the crystallographic a and b axes, respectively. Our measurement of T_N = 14.8K is exactly coincident with the sudden drop in CDW amplitude, suggesting strong coupling between CDW and magnetic order. Temperature evolution of satellite intensities in linear and circularly polarised light found the respective ratio to be invariant with temperature, suggesting a single magnetic phase below T_N. Azimuthal measurements revealed a single helical spin arrangement with an elliptical envelope of m_y/m_z = 1.15. This is unlike the x = 1 material, in which a SDW forms first, transitioning to a helical ground state on cooling. Evidence was found of a small longitudinal component that may have been previously hidden in related materials by multiple sub-micron domains. Future work on the Eu electronic ground state will help understand the effects of Ga substitution on the evolution of the magnetic structure.