According to Wikipedia:
[edit] Collecting magnets as a hobby
Collecting magnets, such as city and county magnets from all around the wolrd, became a popular hobby, as also collecting of many other memorabilia. Many people are bringing refrigerator magnets from cities, sights, places and countries they've been to, because such magnets are popular and inexpensive touristic souvenirs.
Though there is no official term (like numismatics) for collecting magnets, but with a growing interest to this subject there is some approach by collectors to find a proper term. For instance, a russian collector proposes a term memomagnetics (Russian: мемомагнетика), derived from words memoriale (lat.) and magnetis (gr.)[1]. Then a collector of magnets would be called memomagnetist. These terms were accepted by the biggest Russian online community for magnet collectors.[2]
Hope this helped.