The influence of magnetic dilution in the Zn1−xMnxGa2Se4 series with 0.5<x<1

Abstract

The Zn1−xMnxGa2Se4 system with 0.5<x<1, which represents a magnetic dilution of the tetragonal MnGa2Se4, retains the defective chalcopyrite structure of the parent compound. Neutron powderdiffraction experiments and temperature dependent magnetic susceptibility measurements show that such dilution has a significant influence on the magnetic properties of the system. The distance between the closest magnetic atoms decreases from a to a/2√Å (where a is the lattice parameter and a≈5.6Å), making the Curie-Weiss temperature greater than the expected value. The magnetic dilution also decreases the internal distortion, so that the structure becomes closer to that of the ideal zinc-blende arrangement. Although MnGa2Se4 behaves as an antiferromagnet below TC=6.4±0.1K, the magnetic properties of Zn1−xMnxGa2Se4 with 0.5<x<1 suggest a glassy type behavior at low temperatures. This magnetic behavior is found to be compatible with the distribution of the Mn ions within the lattice and can be tuned by tailoring the concentration of magnetic ions. Surprisingly, the magnetically undiluted system corresponding to the Zn1−xMnxGa2Se4 0.5<x<1 series is not MnGa2Se4, a magnetic lattice with a body centered cubic symmetry, but a structure possessing a greater number of sites available to the magnetic ions.