Electronic and structural properties of Laves-phaseMgZn2of varying chemical disorder

Abstract

The C14 Laves-phase ${\text{MgZn}}_{2}$ has been investigated from 30 to $36\text{ }\text{at}\text{.}\text{ }\mathrm{%}\text{ }\text{Mg}$. In this way chemical disorder can be monitored over a limited concentration range and the influence on electron properties can be investigated. Our studies include thermodynamic calculations of atomic configurations of Mg and Zn at off-stoichiometric compositions, electronic-transport measurements, and electronic band-structure calculations of ${\text{MgZn}}_{2}$. The disorder introduced by alloying was found to be substitutional for all C14 alloys, and to have a markedly stronger effect on resistivity and magnetoresistance, $\ensuremath{\Delta}\ensuremath{\rho}(B)/\ensuremath{\rho}(0)$, on the Mg-rich side due to strain introduced when Mg substitutes for Zn. $\ensuremath{\rho}(T)$ and Hall constant were characteristic for weakly disordered binary alloys. $\ensuremath{\Delta}\ensuremath{\rho}/\ensuremath{\rho}$ of ${\text{MgZn}}_{2}$ was large, reached 6 at 4.2 K and 8 T, and decreased strongly at off-stoichiometric compositions. The results are discussed in view of the band-structure results and in terms of relations between atomic order and electronic properties. Several properties were found to resemble pure Zn. An empirical correlation over more than six orders of magnitude in $\ensuremath{\Delta}\ensuremath{\rho}/\ensuremath{\rho}$ was found for Zn and Zn-based alloys.