Observation of itinerant ferromagnetism in layered Sr3Ru2O7 single crystals

ST(3)RU(2)O(7) is a layered compound and a member of the Ruddlesden-Popper-type compound series of S(n+1)RU(n)O(3n+1) (n=1, 2, and n=infinity) with n=2. Single crystals of Sr3Ru2O7 were grown and characterized, providing an unambiguous indication of a rich ferromagnetic state with T-c=104 K and a saturated moment of 1.30+/-0.05 mu(B)/Ru at T=5 K. Among many interesting features, a magnetic spin reorientation transition is observed, suggesting that moments in the ordered state order ferromagnetically with a slight canting on adjacent spins. Negative magnetoresistance, commonly occurring in ferromagnets, is relatively large (19% at 10 T and T=30 K), suggesting a significant suppression of spin-flip scattering by the applied magnetic field. The results are discussed with comparisons drawn with sister compounds Sr2RuO4, SrRuO3 and other related systems.