A nonvolatile memory comprising at least one ferromagnetic region having permittivity which changes from a first state to a second state of lower permittivity upon heating; at least one heater operatively associated with the at least one ferromagnetic region which selectively provides heat to the ferromagnetic region to change its permittivity; and a plurality of connectors operatively connected to the at least one heater and adapted to be connected to a current source that provides a current which causes the heater to change the at least one ferromagnetic region from a first state to a second state. Optionally, the memory is arranged as an array of memory cells. Optionally, each cell has a magnetic field sensor operatively associated therewith. Optionally, the nonvolatile memory is radiation hard. Also, a method of recording data by heating at least one ferromagnetic region to change its permittivity.