Towards universal magnetization curves in the superconducting state ofRuSr2GdCu2O8

The reported dc magnetization measurements on the magnetic ${(T}_{M}\ensuremath{\sim}130\mathrm{K})$ superconductor ${(T}_{c}\ensuremath{\sim}30\mathrm{K})$ ${\mathrm{RuSr}}_{2}{\mathrm{GdCu}}_{2}{\mathrm{O}}_{8}$ (Ru-1212Gd) reveal a variety of behaviors below ${T}_{c}.$ The fact that, for magnetometers which require sample motion during the measurements, artifacts can arise in the measured magnetic moment, when the movement of the sample is done in an inhomogeneous field, complicates even more the analysis of the existing data. In order to avoid the generation of artifacts, we did measurements on a stationary Ru-1212Gd sample employing a homemade magnetometer. The measured curves showed none of the suspicious ``symptoms'' present in the curves measured with a magnetometer employing sample movement, and if verified by measurements on stationary samples by other groups, a universal behavior in the superconducting state of Ru-1212Gd could be revealed by the dc magnetization measurements. Our considerations support the existence of bulk superconductivity for Ru-1212Gd.