Critical scaling analysis of the long-range magnetic interactions and renormalization of magnetic entropy change in Gd12Co7 compound

Abstract

The scaling critical behaviors of Gd12Co7 compound around TC were investigated based on the M-H curves in a magnetic field change of 0–2T. The critical exponents β and γ determined by modified Arrott plot (MAP) and Kouvel–Fisher (KF) methods are [β=0.479(5) and γ=1.004(2)] and [β=0.473(2) and γ=0.983(3)], respectively. The exponents δ derived from Widom scaling relation (MT=TC=163K=DH1δ) and universal relation of the relative cooling power (RCP∝H1+1δ) are δ=3.032(8) and δ=2.903(1). The average values of critical exponent (β=0.476(3), γ=0.993(7), and δ=2.967(9)) are very close to mean-field model (β=0.5, γ=1, and δ=3), which indicates that the magnetic interactions in Gd12Co7 compound are long–range interactions. The average value of critical exponent n for MAP (0.649(1)), KF (0.638(3)), and |ΔSM|∝Hn(0.714(8)) at TC is 0.667(4) and well in agreement with mean field long–range interaction model (n=2/3). The plot M1βvs.(H/M)1γ constructed by above critical exponents fall into two distinct branches above and below TC and completely complies with the scaling hypothesis. At the same time, the normalized curve of magnetic entropy change shows that renormalized magnetic entropy change ΔS′ of Gd12Co7 is mainly determined by a=1.548(1) and b=1.549(3) in Lorentz function.