Influence of Ce substitution on the critical properties of 3D-Heisenberg Cd_xCe_yCr₂Se₄ ferromagnets

Abstract

The critical behaviour of single-crystalline Cd _x Ce _y Cr₂Se₄ spinels investigated around the paramagnetic–ferromagnetic phase transition revealed an increase in the critical exponents from β = 0.359, γ = 1.186, δ = 4.404 at T _C = 131.95 K for Cd_0.96Ce_0.03Cr₂Se₄ to β = 0.382, γ = 1.286, δ = 4.487 at T _C = 133.73 K for Cd_0.83Ce_0.13Cr₂Se₄. These values are close to those predicted by the renormalization-group calculations for a three-dimensional isotropic short-range Heisenberg ferromagnet, although their increase with the Ce substitution suggests a shift towards the mean-field estimates, characteristic of isotropic long-range exchange interactions. These results are being considered in relation to the strong lowering of magnetic moment from 5.67 µ_B/f.u. for y = 0.03 to 3.0 µ_B/f.u. for y = 0.13.

Keywords:

• spinel ferromagnets
• critical properties
• electron paramagnetic resonance

Acknowledgments

The work was supported by the Ministry of Science and Higher Education by the Grants No. N N204 145938 and No. N N202260939.