Nghiên cứu tính chất từ của một số hợp chất đất hiếm - kim loại chuyển tiếp loại mới : Đề tài NCKH. QT.98.06

Đ Ạ I HỌ C Q U Ố C GIA HÀ NỘI T R Ư Ộ N G Đ Ạ I HỌ C K H O A HỌC T ự NH IÊN ********* ĐỀ TÀI: NGHIÊN CỨ U T ÍN H C H Ấ T TỪ CỦA M ỘT số HỢ P C H Ấ T Đ Ấ T H IẾ M - KIM LOẠI C H U Y Ể N t i ế p l o a i m i MÃ SỐ: Q T -98-06 C hủ trì đề tài: PGS T SK H Ngu.vẻn H oàng Lương H À N Ộ I - 2c is the Fe-sublattice ordering temperature and Tfc - Tc for Y3(Fe,M )» systems, CFc is the Curie constant o f the Fesublattice, N u is the number o f Fe atom s per unit volume, kB is the Boitzmann constant The term 2[S*(S*+ 1]i/2ub is the efFective magnetic moment o f the Fe atoms in the paramagnetic State For Fe in R3(Fe,M )29 compounds, the value o f2 [S * (S * + 1]1/2/jb ìs taken as 3.5 Ua on the basis o f a comparison o f the paramagnetic susceptibility o f related R-Fe com pounds (RFe 2, RFes and R2Fei ) [5] In this manner we derived «Fe-Fc = Tf.u.J/JB for the Y 3Fe 2s.s2V 2.1s compound and /7Fc-Fc = 4.8 T ĩ u /mb ths Field (T) Fig.l Magneuzation curves at 4.2 K íor the Y3Fe26.32V:.i3 and Y3Fe28.nn Ino Understanding obtained from studies on melt-spun ribbons will later be applied to studies on buik cast forms o f the maierial Procedure The composition chosen for invesiigation was based on Dubỉỉshed experiments to ỉdentiíy the best glass-íormmg composition in the Nd-Fe-Ai system.^ Samples o f the coEnposition NdéoFe3oAJio were made usúig three diữerent routes Three different pre-ailoyed staning charaes were prcpared bv arc-melting the constituent high-purity elemenis under an atmosphere o f Õ.7 bar high purity Ar in different sequences: Fe and AI vvere combined and Nd ailoyed in later Nd and Fe were combined and AJ added later, and all three elements wére pre-ailoved simuitaneously These three pre-alloymg conditions axe reíeưed to as (Fe,Al)+N