Magnetically ordered and kagome quantum spin liquid states in the Zn-doped claringbullite series

Abstract: Neutron scattering measurements have been performed on deuterated powder samples of claringbullite and Zn-doped claringbullite (Zn$x$Cu${4-x}$(OD)${6}$FCl). At low temperatures, claringbullite Cu$_4$(OD)${6}$FCl forms a distorted pyrochlore lattice with long-range magnetic order and spin-wave-like magnetic excitations. Partial Zn doping leads to the nominal ZnCu$3$(OD)${6}$FCl compound, a geometrically frustrated spin-1/2 kagome antiferromagnet that shows no transition to magnetic order down to 1.5 K. The magnetic excitations form a gapless continuum, a signature of fractional excitations in a quantum spin liquid.