Prefix
A prefix, or combining form, indicating ferrous iron as an ingredient; as, ferrocyanide.
Source: Webster's dictionaryEven if θ is close to zero this does not mean that there are no interactions, just that the aligning ferro- and the anti-aligning antiferromagnetic ones cancel. Source: Internet
The sign of θ depends on whether ferro- or antiferromagnetic interactions dominate and it is seldom exactly zero, except in the dilute, isolated cases mentioned above. Source: Internet