Phase Diagram And Physical Properties In?Sm,Nd?Fe₂ Compounds

RFe₂-type?R=rare earth?giant magnetostrictive alloy is a kind of important functional materials.Terfenol-D(Tb_0.27Dy_0.73Fe₂),as the most representative magnetostrictive materials,has been widely applied in some military fields such as sonars,radars and sensors.The super magnetostriction of Tb_0.27Dy_0.73Fe₂ comes from the anisotropy compensation between TbFe₂ and DyFe₂.Similarly,SmFe₂ possesses the largest negative saturation magnetization of-1560?10^-6which allows it become a possible alternative of Tb_0.27Dy_0.73Fe₂.However,the possibility of application of SmFe₂ is limited by its manufacturing process and price.In this work,by optimizing the process and adjusting the ingredients of the materials,we obtain a large magnetostrictive material which displays a sensitive respond in low magnetic field.First,the phase transition and magnetostriction property of Sm_0.9Nd_0.1Fe₂ were investigated.The mixture of two different phases near the phase transition point of Sm_0.9Nd_0.1Fe₂ was confirmed.Due to the mixture of phases,the magnetostriction of Sm_0.9Nd_0.1Fe₂ around the phase transition point reached a maximum.However,the Curie temperature of Sm_0.9Nd_0.1Fe₂ is 226 K,which is far below room temperature and limits its application.To increase the phase transition temperature and reduce the price,we substitute Nd for Sm in SmFe₂.The phase diagram of Sm_xNd_1-xFe₂ has been obtained.It has been found that when x=0.55 the saturation magnetostriction of it displays an aberration.The high concentration of Nd and good sensitive respond in low magnetic field allow Sm_0.55Nd_0.45Fe₂ to be widely applied.At the last part,the Magnetocaloric effect?MCE?and transition order in Nd(Fe_0.2Co_0.8)₂ single Laves phase were studied by dc magnetization measurement.It was found that Nd(Fe_0.2Co_0.8)₂ with Curie temperature²63 K possesses a moderate entropy change of 1.66 J/kg K but a wide operating temperature range for MCE 102 K and a large refrigerant capacity 169.32 J/kg at an external field change of 3 T.The wide operating temperature range and large refrigerant capacity make Nd(Fe_0.2Co_0.8)₂ become a promising material of refrigeration technology.