What is ZFC-FC?

Answer 1

Zero Field Cooling - Field Cooling

Measuring an effect from a field in the two following ways:

ZFC- Applying the field at a relatively low temperature compared to a characteristic temperature and continuously measuring the effects of the field as you raise the temperature to a level well above the characteristic level.

FC - Applying the field at a relatively high temperature compared to a characteristic temperature and continuously measuring the effects of the field as you lower the temperature to a level well below the characteristic level.

FC can be thought of as the reverse process to ZFC. If the effect you're measuring doesn't reverse using ZFC-FC, then you have something interesting on your hands.

Answer 2

ZFC-FC stands for "Zermelo-Fraenkel set theory with the Axiom of Choice." It is the standard form of set theory used in mathematics, where the Axiom of Choice is assumed to hold. This axiom states that given a collection of non-empty sets, it is possible to choose exactly one element from each set.