NMR INVESTIGATIONS OF YMN2HX HYDRIDES

The YMn2Hx hydrides with x = 1, 2, 3 were investigated by Mn-55 NMR sp in echo measurements at atmospheric and high pressure. Resonance lines at frequencies up to 440 MHz were observed for the hydrides, correspo nding to a huge increase of the hyperfine fields at those Mn with hydr ogen neighbours. At high pressure the initial decrease of the magnitud e of the Mn hyperfine field of YMn2H1 at 4.2 K was found to be 4% per kbar which is an order of magnitude bigger than observed in the other magnetically ordered materials. The effects are interpreted in terms o f changes of the orbital contribution and valence electron contributio n to the hyperfine field caused by hydrogenation and the influence of the external pressure.