La0.67–xDyxPb0.33MnO3（x=0.00 and x=0.10） were elaborated by the solid state method and checked by X-ray diffraction. Close to magnetic temperature transition, the order transition and the critical behavior were inv...La0.67–xDyxPb0.33MnO3（x=0.00 and x=0.10） were elaborated by the solid state method and checked by X-ray diffraction. Close to magnetic temperature transition, the order transition and the critical behavior were investigated by dc magnetization measurements versus x composition. The critical properties were investigated through various techniques such as modified Arrott plot（MAP）, Kouvel-Fisher（KF） method and critical isotherm（CI） analysis based on the data of static magnetic measurements recorded around the Curie temperature TC. The values of critical exponents（β and γ） estimated were found to lie between those predicted for a 3D-Ising model for x=0.00 and those of 3D-Heisenberg model for x=0.10. The reliability of the critical exponent＇s values was confirmed by the Widom scaling relation and the universal scaling hypothesis. The change in the universality class should be due to the increase of the Dy content.展开更多
Hexagonal MnNiGe-based alloys are a series of novel functional materials with potential magnetostructural transitions （MSTs）. Accordingly, it was investigated the magnetic features of bulk hexagonal MnNiGa alloy and...Hexagonal MnNiGe-based alloys are a series of novel functional materials with potential magnetostructural transitions （MSTs）. Accordingly, it was investigated the magnetic features of bulk hexagonal MnNiGa alloy and attempted to partially substitute Mn by Co atoms to tailor its structural and magnetic properties. Nonetheless, the introduction of magnetic Co atom fails to bring about the first-order phase transition and gives rise to the emergence of second phase with cubic structure instead. For ternary MnNiGa parent alloy, the second-order nature of transition is confirmed by both the absence of thermal hysteresis and the standard Arrott plot. To the end, the values of isothermal entropy change are determined by Maxwell relation, and the maximal values follow the trend predicted by the mean-field theory. Its broad transition region （-53 K） leads to only a very small value of entropy change （- 2.4 J·kg^-1·K^- 1 at a field change of 3 T）. In turn, the wide transition ensures a relative large refrigerant capacity （-89.4 J·kg^-1）, which is comparable to that of MnNiGe-based systems. Although the substitution of Co for Mn site is unsuccessful, the chemically modified MnNiGa is still a promising candidate for the application of magnetocaloric effect （MCE） with merits of higher magnetization and better mechanical performance than MnNiGe-based systems.展开更多
文摘La0.67–xDyxPb0.33MnO3（x=0.00 and x=0.10） were elaborated by the solid state method and checked by X-ray diffraction. Close to magnetic temperature transition, the order transition and the critical behavior were investigated by dc magnetization measurements versus x composition. The critical properties were investigated through various techniques such as modified Arrott plot（MAP）, Kouvel-Fisher（KF） method and critical isotherm（CI） analysis based on the data of static magnetic measurements recorded around the Curie temperature TC. The values of critical exponents（β and γ） estimated were found to lie between those predicted for a 3D-Ising model for x=0.00 and those of 3D-Heisenberg model for x=0.10. The reliability of the critical exponent＇s values was confirmed by the Widom scaling relation and the universal scaling hypothesis. The change in the universality class should be due to the increase of the Dy content.
基金supported by the National Natural Science Foundation of China(Nos.11404186, 11364035,51371111 and 11304274)the Applied Basic Research Foundation of Yunnan Province(No.2012FD051)+1 种基金the Project for Innovative Research Team of Qujing Normal University(No. TD201301)the Key Basic Research Program of Science and Technology Commission of Shanghai Municipality(No. 13JC1402400)
文摘Hexagonal MnNiGe-based alloys are a series of novel functional materials with potential magnetostructural transitions （MSTs）. Accordingly, it was investigated the magnetic features of bulk hexagonal MnNiGa alloy and attempted to partially substitute Mn by Co atoms to tailor its structural and magnetic properties. Nonetheless, the introduction of magnetic Co atom fails to bring about the first-order phase transition and gives rise to the emergence of second phase with cubic structure instead. For ternary MnNiGa parent alloy, the second-order nature of transition is confirmed by both the absence of thermal hysteresis and the standard Arrott plot. To the end, the values of isothermal entropy change are determined by Maxwell relation, and the maximal values follow the trend predicted by the mean-field theory. Its broad transition region （-53 K） leads to only a very small value of entropy change （- 2.4 J·kg^-1·K^- 1 at a field change of 3 T）. In turn, the wide transition ensures a relative large refrigerant capacity （-89.4 J·kg^-1）, which is comparable to that of MnNiGe-based systems. Although the substitution of Co for Mn site is unsuccessful, the chemically modified MnNiGa is still a promising candidate for the application of magnetocaloric effect （MCE） with merits of higher magnetization and better mechanical performance than MnNiGe-based systems.
