  We report the synthesis and characterization of a bulk diluted magnetic
semiconductor (La1-xBax)(Zn1-xMnx)AsO (0 <= x <= 0.2) with a layered crystal
structure identical to that of the "1111" FeAs superconductors. No
ferromagnetic order occurs for (Zn,Mn) substitution in the parent compound
LaZnAsO without charge doping. Together with carrier doping via (La,Ba) sub-
stitution, a small amount of Mn substituting for Zn results in ferromagnetic
order with TC up to ~40 K, although the system remains semiconducting. Muon
spin relaxation measurements confirm the development of ferromagnetic order in
the entire volume, with the relationship between the internal field and TC
consistent with the trend found in (Ga,Mn)As, the "111" Li(Zn,Mn)As, and the
"122" (Ba,K)(Zn,Mn)2As2 systems.

Strongly Correlated Electrons;Materials Science