Iron + Sulfur

Iron and sulfur are mixed. When mixed the iron filings retain their magnetic properties.
Next part of that mixture is heated using a meker burner. The mixture becomes a fluid that eventually starts to glow a bright red color. After cooling the test tube is broken to obtain the black solid that was inside. The magnetic properties of the black solid have changed. What is the difference between the mixture of the Fe/S before and after heating at the particle level?

Видео Iron + Sulfur канала Scott Milam