re·ten·tiv·i·ty 
(rē′tĕn-tĭvĭ-tē)
(rē′tĕn-tĭvĭ-tē)n.
1.
a. The quality or state of being retentive.
b. Capacity or power of retaining.
2. Physics The capacity for a body to remain magnetized after the magnetizing field has ceased to exert an effect.