Hydrogen-induced extremely large change in Curie temperatures in layered GdTSiH (T = Mn, Fe, Co)

Magnetic properties of new GdTSiH (T = Mn, Fe, Co) hydrides are reported. Hydrogen insertion in the crystal lattice of GdTSi does not change the space group of these compounds but changes the lattice parameters anisotropically: the c parameter strongly increases, while the a parameter slightly decreases. All the investigated GdTSiH compounds exhibit ferromagnetic ordering at low temperatures. Hydrogenation leads to an extremely large reduction (by hundreds of degrees) of the Curie temperature. In the case of the GdCoSi compound, hydrogen intake changes the type of magnetic ordering from an antiferromagnetic to a ferromagnetic one.