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 powder diffraction 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∕2Å (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.

Order/disorder phenomena in Zn1−xMnxGa2Se4ordered vacancy compounds: high temperature neutron powder diffraction experiments

“…Room temperature parameters obtained in this work are in good agreement with [12] and [13] The dependence of a, c and σ with temperature and composition is attributed to the combined effect of thermal expansion and changes in the degree of structural order, both at the phase transition and before. For chalcopyrite materials it has been shown that anisotropic thermal expansion occurs, yielding in general an increase of the tetragonal distortion with temperature [31].…”

“…As regards the Zn 1-x Mn x Ga 2 Se 4 series, electronic band gap and magnetic properties have been shown to vary non-monotonically with composition [9][10][11], a fact that has been attributed to a varying degree of disorder along the series. This hypothesis has been verified in a structural study performed by means of time of flight (TOF) neutron diffraction at room temperature (RT) [10][11][12][13]. As reported in [10], the degree of order is closely related to the Mn occupancy of the available sites: 2d and 2c (if the space group is I-4) or 4d (if it is I- Mn partially occupies the 2d and 2c sites, resulting in 0< η <1.…”

“…Three diffraction patterns were collected for each sample: one at room temperature (RT) and two at high temperature but close to the phase transition: one (T 1 ) below T c and the other one table 2). The parameters and space groups determined in [12] and [13] were taken as a starting point to fit the RT diffractograms. For the high temperature diffraction patterns, either below or above T c , several space groups were considered, involving different models of cation and vacancy disorder.…”

High-pressure Raman scattering study of defect chalcopyrite and defect stannite ZnGa2Se4

“…To this respect, while some authors claim that ZnGa 2 Se 4 crystallizes in the tetragonal ordered defect chalcopyrite (DC) structure with space group (SG) I-4 [see Fig. 1(a)] where cations and vacancies are completely ordered, 7,13,15,16,22 other authors report that ZnGa 2 Se 4 crystallizes in the partially disordered tetragonal defect stannite (DS) structure, also known as defect famatinite, with SG I-42 m and higher symmetry than the DC phase [8][9][10][11][12]21,26 [see Fig. 1(b)].…”

“…[1][2][3][4] In particular, ZnGa 2 Se 4 has a high photosensitivity and strong luminescence, 2 can be used for phase change memories, 5 and has been proposed as a candidate for electronic device applications forming part of heterojunction diodes. 6 The properties of ZnGa 2 Se 4 have been characterized by x-ray diffraction (XRD), 7,8 neutron and electron diffraction, [9][10][11][12] extended x-ray absorption fine structure, 13 infrared (IR), 14,15 Raman spectroscopy, [15][16][17][18][19][20][21][22][23][24] and magnetic 25 measurements. To this respect, while some authors claim that ZnGa 2 Se 4 crystallizes in the tetragonal ordered defect chalcopyrite (DC) structure with space group (SG) I-4 [see Fig.…”