Decoupling of the magnetic and structural transformations in Er5Si4

The binary Er5Si4 compound, previously classified as a simple ferromagnet with Tc=25K, exhibits an unexpected crystallographic phase transition between 200 and 230 K. As such, the magnetic properties of two crystallographic modifications of Er5Si4 are different, as follows from the differences in their paramagnetic behavior. Thus, exchange interactions appear to be enhanced in the orthorhombic phase, where short Si-Si bonds exist between all slabs.