EFFECTS OF HYDROGEN ABSORPTION ON THE MAGNETIC-PROPERTIES OF Y(CO0.925AL0.075)(2)H-X

The high-field magnetizations of Y(Co0.925Al0.075)(2)H-x have been mea sured for 0 less than or equal to x less than or equal to 3.44 togethe r with those of Y(Co0.94Al0.06)(2) and amorphized YCo2H3.06 in pulsed high magnetic fields up to 42 T. The itinerant metamagnetic transition is broadened, but clearly observed in Y(Co0.925Al0.075)(2)H-x with x less than or equal to 0.72. Hydrogen absorption reduces the critical f ield B-c of the transition. The value of B-c decreases nearly linearly with increasing the lattice parameter a in the region x<0.28, which i s consistent with that due to Al substitution for Co in the parent com pound. The metamagnetic transition disappears in the region n>1.12. A weak spontaneous moment appears in all the hydrides, which originates from a partial structural disordering of the crystal lattice induced b y hydrogen absorption. The hydrogen-amorphized YCo2H3.06 is a strong f erromagnet. The magnetic properties are very similar to those of amorp hous YCo2. (C) 1998 Elsevier Science S.A. All rights reserved.