Comparative investigation of structural and transport properties of L10 NiPt and Copt phases; the role of magnetism

The re\tilt\ 01 :I compar;itivc investigation of strueturiil and transport properties of equiatomic NiPt and C'oPt ph;i\es. in their ordered and disordered states. iire presented and di\cus\etl. The tho compounds displa) the same hind ol order-disorder transforma- tion LI,,-h, in rhcir pir;imagnetic \tate. In thi\ stud!. atrcntion \viis paid to make iiieii\iiremcnts on \ampies in well detined thermod~n,imie state\. U hich can he either equilihriuin statcs or quenched one\. Thi\ in~estig;ition \hi)&\ that the atomic disorder gencr;ited hy the thermal effect or h) con\titution:il deleet\ (o('C-\toichiometr! ) hiis jimilur consequences on the structure (tetragon;ility ratio) irnd on the re\idual rc\istivit) in the tho compounds. A grcat ditt'erence occur\ in the high-Tmistivity. he lo^ and iit the 0-1) translormation temperature (T,),)). Whcre;i\ NiPt displa)s ;I hehakiour typical of this kind of transforina- tion. Copt \how\ unexpected rc\ults. in particular ii decrease in its resistibity ;it To,,. Such ;I dil'lerence can he e.;pl;iincd by taking into account the \pin-disorder \cattcring contribu- tion to the resisti\ity. which I\ larger in Copt than in NiPt. A process hased on the existence ol Huctu;iting Ioc,il magnetic moment\ and magnetic short-range order in the p;iramagnetic state of C'oPt i\ propowd to expl;iin the ohserved hehaviour qualitati\ely.