It would help if you told us why you want to get rid of the hawks.
Crows do not deter hawks. They share territories.
Crows and other bird species will chase hawks away from their nests and babies, often working in groups - called mobbing. However, they don't need a group. Even one small bird can harass a larger bird, and force it to leave the immediate area. That does not mean that the hawk leaves the territory, it will always be a threat, and will return.
Here's the problem...as long as you have any bird population, including crows...you will have birds of prey. Hawks and falcons eat other birds, including fledgling crows.
Further, if you begin feeding to attract crows - you will attract other birds and animals, which will attract more birds of prey, as they feed on the animals you are feeding.
It's a viscious cycle.
I'm not sure what you are trying to protect. If you trying to protect your own domestic animals, you should take other precautions, such as keeping chickens, pigeons, or other small pets in secure housing, inaccessible to any kind of predator.
If you are concerned about the wildlife in your yard, don't bother. Nature should be left alone. Predation among wild species is normal, and should be expected.
Btw - crows are predators, they raid the nests of other birds.
It's best to leave nature alone, and adapt to it - rather than try to change it.