Estudo de propriedades estruturais e magnéticas em compostos de Ca(2-x)A(x)MnRe06COM A=Y, Ce

Abstract

A study was carried out on the effects of chemical pressure and hydrostatic external pressure on structural and magnetic properties in Ca (2-x) A (x) MnReO6 compounds with A = Y, Ce. Chemical pressure was achieved by doping this compound with cerium and yttrium by means of a solid state reaction using the encapsulated quartz tube technique. The structural characterization through the Rietveld analysis of the X-ray diffraction pattern showed that the samples obtained are monophasic with 5% cerium, 5% and 15% yttrium. The structural analysis also showed that the unit cell undergoes an expansion with doping without a change in symmetry. The X-ray absorption spectra at the K edge of Mn and L3 of Re showed that Mn and Re assume mixed valence in all samples. In XANES measurements under pressure, no variation in valence for Mn was observed. However, a displacement of the L3 edge of Re for high energy was observed as a function of the pressure applied to the sample doped with cerium. In the sample with yttrium, the displacement of the L3 absorption edge of the Re occurred at low energies. The compound's frustration temperature decreased from 119.44 K to 113.57 K when doping with cerium. However, when doping is done with 15% yttrium, the frustration temperature increases from 119.44 K to 141.77 K. The frustration temperature increased for all samples with the application of hydrostatic pressure, however this increase was an average of 2.6 K. The main conclusion was that the chemical pressure does not have the same effect as the external hydrostatic pressure in the compounds of Ca (2-x) A (x) MnReO6 with A = Y and Ce, considering evolution of the frustration temperature derivative with doping, when compared to the effect of hydrostatic pressure