EFFECT OF ATOMIC ORDER ON SOME PHYSICAL-PROPERTIES OF CO25PT75

Co25Pt75 alloy was made by the induction melting method. In order to a chieve various degrees of atomic order in the sample, annealing and qu enching techniques were employed. We are interested in studying how at omic order would affect the physical properties of CoPt3, such as its lattice constant, thermal expansion coefficient, specific heat, and el ectrical resistivity. It is found that, on ordering in CoPt3 the f.c.c . lattice expands isotropically. Correspondingly, the sample length sh rinks when temperature is raised above the order-disorder transition t emperature T-x. Both the high temperature resistivity and the specific heat data indicate that the CoPt3 system does not have a gap-type beh aviour. Around T-x, as well as the long-range order, there may exist a short-range order in CoPt3, as implied from the resistivity measureme nt.