Magnetothermal effect, phase transition and critical behavior of Mn5Ge3-xVx alloys

In this paper, the magnetocaloric properties, phase transitions, and critical properties of Mn5Ge3-xVx (x = 0.1, 0.2, and 0.3) compounds prepared by arc melting were investigated. The incorporation of V in Mn5Ge3-xVx alloys leads to a reduction in both the Curie temperature and the magnetic entropy change. Analysis of the isothermal magnetization curves using common methods such as Arrott curves, normalized curves, and Landau theory reveals that the system undergoes a second-order phase transition. Furthermore, the temperature-averaged entropy change (TEC) at 1-7T fields and the field hysteresis loss (HL) at 7T were calculate. The study then employs a modified Arrott diagram, the Kouvel-Fisher method, and critical isotherm curves to examine the critical behavior in the vicinity of the phase transition. Additionally, the accuracy of these critical exponents using Widom's scaling laws and scaling equations were validated. Further analysis results indicate that the spin coupling in the phase transition of Mn5Ge3-xVx exhibits 3D Ising behavior, characterized by magnetic exchange decay rates of J(r) approximate to r(-4.83), r(-4.75), and r(-4.77). These spin interactions are of the short-range extension type beyond the nearest neighbors, and the spin interactions extend beyond the nearest neighbors, potentially related to the Mn-Mn interactions with varying exchange strength magnitudes.