Electrical and Magnetic Characterization οf ZnCr_2-xV_xSe₄Spinel Semiconductors

Abstract

Single crystals of ZnCr 2 Se 4 spinel doped with vanadium were prepared by chemical vapour transport. The chemical compositions of three crystals have been determined by X-ray diffraction. The structure refinement using the SHELXL-93 program system determine the cation distribution in the system as ZnCr 2−x V x Se 4 . For x values equal to 0.03, 0.1 and 0.13 the observed symmetry was cubic, space group F d3m. Based on the structural data, influence of the V ions on the magnetic and electrical properties has been analyzed.

Electron Diffraction Reinvestigation of CdCr₂Se₄ and ZnCr_2-xV_xSe₄ Spinel Structures

“…Inspection of the reciprocal space showed that no additional satellite reflections or diffuse scattering are observed. Lattice parameters directly determined for both spinel samples (10.491 Å for ZnCr 2-x V x Se 4 and 11.363 Å for CdCr 2 Se 4 ) differs somewhat from the lattice parameters reported in the literature [11,4]. The accuracy of cell parameters determination from tilt series of electron diffraction patterns is influenced by the calibration procedures and other systematic errors during data reduction process (locating of the centre of individual diffraction pattern, correction for the tilt of rotation axis and background correction).…”

“…CdCr 2 Se 4 is ferromagnetic (T C =142 K) [2] and ZnCr 2 Se 4 is antiferromagnetic (T N =20 K) and below T N shows an interesting and complex helimagnetic spin order [3]. T N of ZnCr 2 Se 4 system doped with V shifts in to lower temperatures with increasing vanadium content [4] Automated electron Diffraction Tomography (ADT) is a recently developed method for electron diffraction acquisition and analysis [5][6][7]. Differently from traditional acquisition based on oriented patterns, ADT is able to sample the whole reciprocal space inside the tilt range of the microscope and to reduce dynamical effects, so that intensity data can be used for ab-initio structure determination by a simple kinematical approximation (I~F 2 ).…”

The ESR study of single crystal spinel ZnCr2Se4 diluted with Sb and V

“…This behavior is accompanied by shift of the resonance field as compared to the high-temperature value. At the same time, the spin susceptibility (DI) rapidly increases and exhibits a broad maximum at T 0 , well above the ordering temperature determined from magnetic susceptibility experiments [21,23]. At the temperature range from 40 K to 20 K the linewidth increase produces a rapid diminution in the intensity and the spectrum is not longer observed below 17 -20 K. The observed behavior of the linewidth and resonance field is attributed to critical phenomena while approaching the antiferromagnetic order.…”

“…Recently, the structural and magnetic investigations of ZnCr 2 Se 4 spinel doped with Sb and V ions were carried out [21][22][23]. The structure refinement was performed using the SHELXL-97 program package showing that all single crystals under study have cubic structure with the space group Fd…”