The spin excitations in alpha-Cu3Mg(OH)6Br2

The two-dimensional (2D) spin-1/2 kagome model has been a subject of intense theoretical study due to its rich ground states. While many of these materials show antiferromagnetic correlations, ferromangetism is rare to find. Recently, we have successfully synthesized a new kagome material alpha-Cu3Mg(OH)6Br2, the spin arrangement along c-axis is antiferromagnetic, that within the kagome plane is ferromagnetic. The specific-heat measurement reveals an upturn behavior of the specific heat is found below 0.2 K, which can be fitted as C~T^-3/2. It is not from the nuclear Schottky anomaly or magnetic impurities since it does not move to higher temperature under magnetic fields. Instead, it is suppressed at 3 Tesla, It indicates that some exotic spin excitations present. So we propose to study the spin excitations in alpha-Cu3Mg(OH)6Br2 down to 30 mK and magnetic field up to 3 Tesla.