Critical properties of the 3D-Heisenberg ferromagnet CdCr₂Se₄

¹ High Magnetic Field Laboratory, Chinese Academy of Sciences - Hefei 230031, PRC
² College of Science, Nanjing University of Aeronautics and Astronautics - Nanjing 210016, PRC
³ Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China Hefei 230026, PRC
⁴ Department of Physics and Electronic Engineering, Hefei Normal University - Hefei 230061, PRC

^a zhanglei@hmfl.ac.cn

Received: 15 August 2010
Accepted: 18 August 2010

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 ß =0.337±0.03 and γ=1.296±0.109 at T_C=130.48±0.34 are obtained. In addition, the critical exponent δ=4.761±0.129 is determined separately from the isothermal magnetization at T_C. 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 T_C collapses into two curves obeying the single scaling equation M(H, ε)=ε^βf_±(H/ε^β+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.