Critical properties of the 3D-Heisenberg ferromagnet \chem{CdCr_{2}Se_{4}}

Abstract

The critical properties of the ferromagnet CdCr2Se4 around the paramagnetic-ferromagnetic phase transition have been investigated. It is found that the 3D-Heisenberg model is the best one to describe the critical phenomena around the critical point. Critical exponents β=0.337±0.03 and γ=1.296±0.109 at TC=130.48±0.34 are obtained. In addition, the critical exponent δ=4.761±0.129 is determined separately from the isothermal magnetization at TC. These critical exponents fulfill the Widom scaling relation δ=1+γ/β. Based on these critical exponents, the magnetization-field-temperature (M-H-T) data around TC collapses into two curves obeying the single scaling equation M(H, ε)=εβf±(H/εβ+γ). Although the 3D-Heisenberg model is the most satisfactory model to describe this system, critical exponents for CdCr2Se4 are slightly smaller than the theoretical exponents (β=0.36, γ=1.39 and δ=4.8). This indicates that the exchange interaction J(r) decays slower than r− 5 in this system, which can be attributed to the spin-lattice coupling.