I have been given this magnetization curve of a molecule- based material with Copper ions present. In general, when applied field (T) increases initially, the sample magnetization increases and reaches a peak. Then it decreases as applied field keeps increasing. When the applied field is negative, the sample magnetization decreases and reaches a point initially, then the curve reverses and starts increasing in magnetization of the sample in the negative direction. What is the reason for this behaviour? what is the oxidation state for Copper ions?