Linear magnetoelastic coupling and magnetic phase diagrams of the buckled-kagomé antiferromagnet Cu$_3$Bi(SeO$_3$)$_2$O$_2$Cl

Abstract

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$_{\mathrm{N}} = 26.4(3)$ K. Grüneisen analysis reveals moderate effects of uniaxial pressure on T$_{\mathrm{N}}$, of $1.8(4)$ K/GPa, $-0.62(15)$ K/GPa and $0.33(10)$ K/GPa for $p \parallel a$, $b$, and $c$, respectively. Below 22 K, Grüneisen scaling fails which implies the presence of competing interactions. The structural phase transition at T$_{\mathrm{S}} = 120.7(5)$ K is much more sensitive to uniaxial pressure than T$_{\mathrm{N}}$, with strong effects of up to $27(3)$ K/GPa ($p \parallel c$). Magnetostriction and magnetization measurements reveal a linear magnetoelastic coupling for $B\parallel c$ below T$_{\mathrm{N}}$, 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.