Most of MagicConan14's fanfics have magica in them. However, to understand what's going on, you'll need to know about Detective Conan/Case Closed, as that is the specific category she mostly restricts herself to.
http://www.fanfiction.net/s/8269574/1/Best-of-Luck-Tantei-kun - This fic is about fallen archangels. They're a bit different to magica.
http://www.fanfiction.net/s/8277678/1/Stealing-Stars - This fic is about angels and demons which are not magica but kinda similar.
http://www.fanfiction.net/s/7751596/1/Disappear - This one involves ghosts working on the same principles as magica.
http://www.fanfiction.net/s/8284216/1/Prophecy - The protagonists may not be magica, but they can still use magic!
http://www.fanfiction.net/s/8877334/1/Disintegrate - This is her newest fic as of 5/1/13.
Christmas specials: http://www.fanfiction.net/s/7607777/1/Rans-Christmas-Wish