Angular-dependent torque magnetometry on single-crystal HgBa2CuO4+y near the critical temperature

Angular-dependent torque magnetization measurements an a HgBa2CuO4+y microc rystal performed close to the critical temperature T-c are analyzed within the framework of three-dimensional (3D) XY critical behavior. In a finite m agnetic field the magnetic torque is given by the derivative of a universal scaling function dG(z)/dz, where the scaling argument z depends on tempera ture, field, and the angle between the field and the c axis of the sample. We are able to determine dG/dz quantitatively by scaling the angular-depend ent torque data. Universal constants and critical amplitudes for HgBa2CuO4y are calculated. [S0163-1829(99)03425-6].