The area of North Atlanta can be referring to 2 different areas. If you google the area, the Map places this area just a bit north and East of the Heart of the City.
Here in Georgia, and as a Real Estate Agent, we tend to call North Atlanta the Cities that are located in the area above The Perimeter loop of 285. These Cities include:
Alpharetta
Berkeley Lake
Buford
Canton
Cumming
Duluth
Dunwoody
Holly Springs
Johns Creek
Kennesaw
Marietta
Milton
Mountain Park
Norcross
Roswell
Sandy Springs
Suwanee
Woodstock