Magnetic and structural studies of Mg2Fe(x)Si(1-x) – hydrides

Mg2Fe(x)Si(1-x) – hydride is a promising multifunctional material in terms of magnetic applications due to a dramatic change in their magnetic, optical and electronic properties upon hydrogen loading. Therefore they are capable of potential applications, e.g. hydrogen sensors for use as safety monitors wherever hydrogen is used, stored, or produced and storage devices.
In order to understand the physical background of Mg2(FeSi) based systems as well as their hydrides, comprehensive investigations were performed on as-grown and hydrogen loaded 250 nm thick Mg2Fe(x)Si(1-x) (x= 0; 0.25; 0.50; 0.75; 0.90; 1.00) films using magnetometry, X-ray diffraction (XRD) and positron annihilation spectroscopy (PAS).
Magnetometry results revealed that upon hydrogen loading volume magnetic properties of the system transforms from superparamagnetic- and spin glass-like behavior to ferromagnetic behavior with high Curie temperature. Likewise, it is found that the hydrogen loading and Fe concentration have direct consequences on the structural properties, these can be explained either by an amorphisation process or by the formation of very small nanocrystalline particles probed by XRD measurements. Furthermore, different sizes and chemical decoration of open-volume defects has been observed by PAS.
The knowledge gained from these studies can be use for monitoring those characteristics that change in the presence of hydrogen.