Phase transitions are generally a collective phenomenon changing the order of a system of atoms, ions, or molecules. This collective change e.g. of a crystal structure or magnetic order into another is accompanied by symmetry changes on a global scale. The symmetry change then also affects the local order. Lattice atoms are subject to this new order according to their respective lattice site.
Defects may partly resist this change of order at the local scale. This is partly their role in alloying and defect tuned instabilities.
In this contribution we display the fields that are experienced by local defects as a result of a set of phase transitions in bismuth ferrite, BiFeO$_3$. To this purpose the somewhat exotic method of gamma-gamma angular correlations is used. On the poster we will explain the method and the results on the coupling of magnetic and electric order at the local scale. The amazingly large magnetoelectric coupling for a single atom is discussed for this antiferromagnetic system. We also show that a considerable number of defects is decorated with adjacent vacancies.