Potrait lens for crop sensor (nikon) camera?

I'm currently using a d5300 and would like to be able to take better potraits.

Currently i own the nikon 35mm 1.8 and the sigma 17-50 2.8

I would like to purchase a lens that could give me more shallow depth of field that the lens i currently own.

I'm leaning towards the 70-200 2.8 from tamron for verstility but also interested in the sigma 85mm 1.4 or 50mm 1.4

Would the 70-200 be good enough to give me a shallow depth of field for outdoor FULL BODY potrait? Or would i need a 85mm/50mm 1.4.

The wider the aperture and the longer the focal length the shallower the depth of field, yes. Remember, though, that it's only useful if you expose at full aperture (manual or aperture priority mode). As for which lens to buy, you have the choice of spending a lot of money or an enormous amount of money. If you can afford it then the 70-200 2.8 lens will do a lot of telephoto work as well as portraits. If it's just for portraits then the 85mm 1.4 will be more than adequate.

You own a cropped sensor camera so a portrait lens is going to be a medium telephoto lens like a 50 mm f/1.8 or f/1.4, a 60 mm f/2.8 (macro) or 85 mm f/1.8 or f/1.4

Actually, the Sigma 17-50 mm f/2.8 should be able to create excellent portraits when set at 50 mm and with the aperture wide open.

I own a Nikkor 70-200 mm f/2.8 lens, however, r I rarely use it to shoot portraits. Its primary job is to shoot sports and action.

The link below is a sample of how I use that lens

Outdoor full body portraits? The 35mm f/1.8 is perfect for that already! To maximize blurring effect, make sure the background is really way far behind and that you stay as close as possible to the subject.