The synthesis and characterization of 1 1 1 1 type diluted ferromagnetic semiconductor (La1-x Ca x )(Zn1-x Mn x )AsO.

We report the synthesis and characterization of a bulk form diluted magnetic semiconductor, (La1-xCax)(Zn1-yMny) AsO, with a layered crystal structure isostructural to that of the 1 1 1 1 type Fe-based high-temperature superconductor LaFeAsO and the antiferromagnetic LaMnAsO. With Ca and Mn codoping into LaZnAsO, the ferromagnetic ordering occurs below the Curie temperature T-C similar to 30 K. Taking advantage of the decoupled charge and spin doping, we investigate the influence of carrier concentration on the ferromagnetic ordering state. For a fixed Mn concentration of 10%, TC increases from 24 K to 30 K when the Ca concentration increases from 5% to 10%. Further increase of Ca concentration reduces both the coercive field and saturation moment. Muon spin relaxation measurements confirm the ferromagnetically ordered state, and clearly demonstrate that (La1-xCax)(Zn1-yMny) AsO shares a common mechanism for the ferromagnetic exchange interaction with (Ga, Mn) As. Neutron scattering measurements show no structural transition in (La0.90Ca0.10)(Zn0.90Mn0.10) AsO below 300 K.