thermoremanent
adjective
ther·mo·rem·a·nent ˌthər-mō-ˈre-mə-nənt 
: being or relating to magnetic remanence (as in a rock cooled from a molten state or in a baked clay object containing magnetic minerals) that indicates the strength and direction of the earth's magnetic field at a former time
thermoremanence
ˌthər-mō-ˈre-mə-nən(t)s
noun 
Word History
First Known Use
1951, in the meaning defined above