Thermodynamic, transport and magnetic properties of the ferromagnetic superconductor RuSr2GdCu2O8 and related compounds

The transport, magnetic and thermodynamic properties of RuSr2GdCu2O8 and re lated compounds are reviewed. These indicate uniform coexistence of superco nductivity (T-c=46K) and ferromagnetism (T-M=132K) in which the former aris es in the CuO2 planes and the latter in the RuO2 planes. The earliest data indicated a typical underdoped cuprate with local Ru moment ferromagnetism, the absence of pairbreaking and transport properties dominated by the CuO2 planes. However, recent results suggest a more complex scenario of itinera nt ferromagnetism and exchange coupling between the CuO2 and RuO2 layers.