HYSTERESIS IN MMNI(5) SYSTEMS WITH ALUMINUM, MANGANESE AND TIN SUBSTITUTIONS

Hysteresis during hydride formation and decomposition in intermetallic compounds of composition MmNi(5-x)M(x), using Indian mischmetal (Mm) containing (in wt%) 43 Ce, 23 La, 18 Nd, 5 Pr, 3 Sm and 8 Fe has been studied. The compositions studied were MmNi(5-x)Al(x) (x = 0.4 and 0.8 ), MmNi(5-x)Mn(x) (x = 0.4 and 0.8) and MmNi(5-x)Sn(x) (x = 0.4). The free energy loss per hysteresis cycle has been obtained from the press ure-composition (PC) isotherms. The partial substitution of nickel wit h aluminium, manganese and tin in MmNi(5) resulted in the lowering of hysteresis loss of pure MmNi(5). Hysteresis loss generally decreased w ith increasing temperature. Annealing generally increased the hysteres is loss at any fixed temperature. The origin for these observations ha s been explained by considering the theories of hysteresis.