Some magnetic properties of platinum-rich Pt-Fe alloys

2014 Measurements of magnetic susceptibility and spontaneous magnetization on face centred cubic platinum-iron alloys having compositions around Pt3Fe and also on alloys with lower iron contents, are reported. In the Pt3Fe superlattice region the alloys appear to be antiferromagnetic when ordered and ferromagnetic when disordered. The more dilute alloys are ferromagnetic, even down to 2 at. % of iron. LE JOURNAL DE PHYSIQUE ET LE RADIUM TOME 20, FFVRIER-MARS 1959, The existence of superlattices iri platinum-rich solid solution alloys containing chromium, manganese or iron has been known for some time. In each case, the face-centred cubic solid solution based on platinum extends from 0 % to well above 25 % of the solute. The superlattices all exist’over a range of composition, with maximum ordering at the 25 % composition, and are of the AuCU3 type. They are stable up to temperatures of the order of 700 OC and above, and are easily formed. Ferromagnetism has been previously detected in the platinum-rich solid solutions, by Friedrich and Kussman (1935) for the platinum-chromium system, by Auwârter and Kussman (1950) for platinum-manganese, and Kussman and von Rittberg (1950) for platinum-iron. In the two systems platinum-chromium and platinum-manganese the strongest ferromagnetic effects were reported to occur near the composition of maximum superlattice. For platinum-iron, however, the 25 % alloy was found not to be ferromagnetic under the conditions used by Kussman and von Rittberg : the ferromagnetic properties developed on both sides of this composition. In the present work, the magnetic susceptibility of various platinum-iron alloys near the Pt 3Fe composition has been measured as a function of temperature. It has been found that in general the Curie-Weiss Law is obeyed at high temperatures, extrapoJating towards a paramagnetic Curie point 0p which depends on composition. The observations are typified by the results shown in fig. 1, which! refer to an annealed alloy containing 26.3 atomic percent of iron. In this case 0p is about 90 °K. On cooling this alloy below room temperature, deviations from the Curie-Weiss Law begin at abont 200 OK. The susceptibility rises to a distinct maximum at 105 °K, and then falls at lower temperatures. At about 50 DK another increase in susceptibility begins. In most cases, susceptibilities were measured in an Fie. 1. Susceptibility of annealed 26.3 % PtFe alloy. applied field of 8.2 kilo-oersteds. In the alloy to which fig. 1 refers, measurements were also made in a range of field strengths between 2.5 and 10. 8 kilo-oersteds at temperatures of 20°, 80°, 200° and 290 ’OK. No significant variation of thé sosArticle published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphysrad:01959002002-3043500