Cranmer, a former global executive director at Dentsu Aegis Network, is Magnetic’s first appointment following the arrival of Sue Todd as its chief executive last year.
He will help UK consumer publishers better promote their brands and products to agencies and advertisers.
Cranmer said: "Our role is to convey the compelling effectiveness of this audience relationship in today’s dynamic media market. There is much to be optimistic about for magazines as quality content increasingly becomes the decisive battleground for attention. We have a wonderful story to tell."
Magnetic has also hired Jo Tomlin as its communications director.
Todd said: "We’re looking forward to working in a new way with advertisers to show the return that can be gained by investing in some of the most trusted and valued content spaces in UK advertising."
The PPA, the magazine trade body, has made its marketing director, James Papworth, redundant following the launch of Magnetic.