Disorder-induced ferromagnetism in CaRuo₃

The magnetic ground state of perovskite structure CaRuo₃ has been enigmatic for decades. Here we show that paramagnetic CaRuo₃ can be made ferromagnetic by very small amounts of partial substitution of Ru by Ti. Magnetic hysteresis loops are observed at 5 K for as little as 2% Ti substitution. Ti is nonmagnetic and isovalent with Ru, indicating that the primary effect of the substitution is the disruption of the magnetic ground state of CaRuo₃ through disorder. The data suggest that CaRuo₃ is poised at a critical point between ferromagnetic and paramagnetic ground states.