An electron paramagnetic resonance study of n-type Zn1−xMnxO: A diluted magnetic semiconductor

We present the results of an electron paramagnetic resonance study of homogeneous single phase Zn1−xMnxO thin films with Mn concentrations varying between x=0.07 and x=0.34. Our results show antiferromagnetic (AF) coupling in the entire concentration range with an effective exchange integral of J∕kB=−21.8K for x⩽0.16 much stronger than in the CdMn(S,Se,Te) series. We observe deviations from the Curie-Weiss behavior for concentrations above x=0.16 and show this to be a “universal” behavior of II-VI diluted magnetic semiconductors. Our results demonstrate that AF interactions are dominating in n-type Zn1−xMnxO (x>0.07) with a carrier concentration of 1018cm−3 contrary to previous claims. These AF interactions are responsible for high spin freezing temperatures and absence of magnetic long range order.