Linear magnetoelastic coupling and magnetic phase diagrams of the buckled-kagomé antiferromagnet Cu_3Bi(SeO_3)_2O_2Cl

Single crystals of Cu _3 Bi(SeO _3 ) _2 O _2 Cl were investigated using high-resolution capacitance dilatometry in magnetic fields up to 15 T. Pronounced magnetoelastic coupling is found upon evolution of long-range antiferromagnetic order at T_N = 26.4(3) K. Grüneisen analysis reveals moderate effects of uniaxial pressure on T_N , of 1.8(4) K/GPa, -0.62(15) K/GPa and 0.33(10) K/GPa for p ∥ a , b , and c , respectively. Below 22 K Grüneisen scaling fails which implies the presence of competing interactions. The structural phase transition at T_S = 120.7(5) K is much more sensitive to uniaxial pressure than T_N , with strong effects of up to 27(3) K/GPa ( p ∥ c ). Magnetostriction and magnetization measurements reveal a linear magnetoelastic coupling for B∥ c below T_N , as well as a mixed phase behavior above the tricritical point around 0.4 T. An analysis of the critical behavior in zero-field points to three-dimensional (3D) Ising-like magnetic ordering. In addition, the magnetic phase diagrams for fields along the main crystalline axes are reported.