Hydrogen ordering induced resistivity anomalies in the superstoichiometric light rare-earth dihydrides

The ordering superstoichiometric light rare-earth dihydrides MH2+c (M-La, Ce; H-hydrogen atoms) characterized by two long-range order parameters, η1 and η2, are considered. The electroresistivity RH associated with the redistribution of hydrogen atoms during the ordering processes is investigated. An analytical expression describing dependence of RH on the equilibrium values of order parameters is obtained. It is shown that in the disorder-order and order-order transition points, the resistivity temperature dependences RH(T) reveal the discontinuity- or kink-like anomalies. Residual resistivity and the possible quenching effect concentration dependences are given.