THE ANOMALOUS TEMPERATURE-DEPENDENCE OF THE PARAMAGNETIC RESPONSE OF FE-RICH FCC FE-NI

Temperature dependent paramagnetic neutron scattering experiments on f ee Fe100-xNix anti-Invar alloys (0 less than or equal to x less than o r equal to 30 at%) show strong magnetic scattering in the foreward dir ection at temperatures as high as 1100 K, indicating ferromagnetic cor relations although, no long-range ferromagnetic ordering occurs in the fee state of the alloys with x less than or equal to 25 at%. The inte nsity of the magnetic scattering in the foreward direction decreases w ith increasing temperature for x = 20 and 25 at%, it remains nearly co nstant with temperature for x = 15 at% and shows the unusual behavior of increasing with increasing temperature for x = 10 at%. The temperat ure dependence:of the correlation length also behaves similarly.