Critical phenomenon in the room-temperature ferromagnet Ce0.65Mg0.35Co3 prepared by high-pressure annealing
Numerous studies have yielded evidence that high-pressure annealing (HPA) can modify the crystal and electronic structure significantly, which thus probably alter the magnetic ordering with a different universality class. In this work, we investigate the effects of HPA on critical behaviors of magnetization in the room-temperature ferromagnet Ce0.65Mg0.35Co3. We observe the HPA compound after annealing at 2 GPa undergoing a second-order phase transition with a decreased Curie temperature. Using the DC magnetization data, the critical exponents β, γ and δ are calculated independently by three methods including modified Arrott plot, Kouvel-Fisher plot, and critical isotherm analysis. The obtained critical parameters together with magnetization data obeys the scaling equation of state, indicating they are intrinsic and unambiguous. Further more, we notice that HPA not only reduces the intensity of exchange coupling, but also elongates the exchange range with J(r)∼r^(-4.467), which leads to a universality class different from the conventional compound and the existing theoretical models.