Magnetic and transport and structure properties of the room temperature ferromagneto Sr1-xHoxCoO3-δ.

The perovskite Sr1-xHoxCoO3-δ shows room temperature ferromagnetism (Tc∼335 K) in a severely limited composition range 0.2<=x<=0.25. The formal Co valence is almost constant at +3 regardless of the Ho concentration (x>=0.2); thus, the high-spin state or the intermediate spin state of 3d6 Co should be mainly responsible for the magnetism. The ferromagnetism was found to accompany the formation of a superstructure 2ap×2ap×4ap (ap denotes a cubic perovskite cell). Besides, an additional superstructure 4(2ap)×4(2ap)×(4ap) was found at x=0.225, where the ferromagnetic volume in magnetic susceptibility was largest. The data suggest that the formation of the multiple superstructures probably plays a key role to establish the peculiar ferromagnetism. [ABSTRACT FROM AUTHOR]