Effect of hydrogen absorption on the magnetic properties of ZrMn 2− xFe x ternaries with a C14 structure

Abstract

Magnetization measurements were carried out on ZrMn 2− x Fe x ( x = 0.4, 0.7 and 1.0) and their hydrides. All systems possess a hexagonal Laves phase structure (C14 structure). These compounds are found to absorb about 3.6 hydrogen atoms per formula unit. The hydrogen absorption is accompanied by a large expansion in volume ranging from 26% to 28% with no change in crystal structure. In this system, both the magnetic moments and the transition temperatures were found to be significantly larger in the hydride phases than in the corresponding host compounds. An increase in the magnetic moments on hydrogenation can be interpreted as a result of charge transfer from the transition metal atoms to hydrogen due to the difference of electronegativity. An increase in the magnetic ordering temperatures is attributed to a decrease in the electron concentration of 3d bands as well as to an increase in the lattice constants on hydrogenation. Spin glass behavior is exhibited by all the systems studied. The spin glass behavior is thought to originate from iron-rich clusters which occur as a consequence of statistical fluctuations in the manganese sublattice.