When utilizing "artificial gravity" generated through a rotating structure using centripetal force, i.e. a centrifuge, is there a minimum diameter or some other attribute that causes or helps alleviate any kind of nausea or motion sickness in humans?
The problem is about a so called 'comfort zone'. In fact it is not radius but a ratio of radius and angular velocity. Nausea or motion sickness is caused mostly by Coriolis acceleration which makes 'artificial gravity' different form nearly homogeneous earth gravity.
There is a real expert on topic Theodore W. Hall. Among a lot of staff about artificial gravity he published an
which may provides the best answer of the question.
Direct answer if your question is R<12 meters or <60 m for 1 g.
By the way, it is what the quality Sci-Fi movies lake 'Odyssey 2001' depicted. Arthur Clark and Stanley Kubrick have had some info on topic.
Is there a minimum diameter? Yes. Every study I've come across agrees on that.
What is that minimum diameter? As I found while answering this question over on WorldBuilding.SE, there's quite a bit of disagreement there. Allowable minimum diameters vary from as high as 180 km to as low as 8 meters.