In my plot, the heroine has to solve incidents caused by curses, supernatural creatures all due to barrier and talisman she uses for her powers, How to set up the magical barrier separating the mundane from the magic
A barrier as in, say, the Mist from Percy Jackson? The stuff that prevents mortal (or, in your case, nonmagical) entities from seeing magical things? I would base it off of whatever culture this takes place in or whatever magic system you are using when it comes to naming it. Other than that, be consistent for those who can and can't see things going on. People may see the effects of magic, but they won't always see the magic happening unless they are able through whatever story reason or MacGuffin you give them.