Experimental measurements of the heats of formation of Fe3Pt, FePt, and FePt3 using differential scanning calorimetry

Abstract

Using differential scanning calorimetry (DSC), the heats of formation of Fe3Pt, FePt, and FePt3 were determined from the reaction of sputter deposited Fe/Pt multilayer thin-films with a periodicity of 200 nm but different overall compositions. Film compositions were measured by energy dispersive x-ray spectrometry. The phases present along the reaction path were identified by x-ray diffraction. For the most Fe-rich phase, namely, Fe3Pt, the measured enthalpy of formation was −9.3 ± 1.3 kJ/mol in a film with a composition of 70.4:29.6 (±0.2 at. %) Fe:Pt. For FePt, the measured enthalpy of formation was −27.2 ± 2.2 kJ/g-atom in a 49.0:51.0 (±0.5 at. %) Fe:Pt film. For FePt3, which is the most Pt rich intermetallic phase, the measured enthalpy of formation was −23.7 ± 2.2 in a film with a composition of 22.2:77.8 (±0.6 at. %) Fe:Pt. The reaction enthalpies for films with Fe:Pt compositions of 44.5:55.5 (±0.3 at. %) and 38.5:61.5 (±0.4 at. %) were −26.9 ± 1.0 and −26.6 ± 0.6 kJ/g-atom, respectively, which taken together with the value for the 49.0:51.0 film demonstrate the relative insensitivity of the reaction enthalpy to film composition over a broad composition range in the vicinity of the equiatomic composition. The experimental heats of formation are compared with two sets of reported first-principles calculated values for each of the three phases at exact stoichiometry.

Tuning crystal structure and magnetic property of dispersible FePt intermetallic nanoparticles

“…6c, d, the signal intensity of the images changes drastically with the variation of Fe concentration for both arrays. Transverse relaxivity (r 2 20 Pt 80 (or A1-FePt NPs) due to their higher magnetization (Fig. 6c-f), which demonstrates that FePt intermetallic NPs can be applied as a potential T 2 contrast agent for MRI.…”

“…To date, most studies on FePt intermetallics with tun-able crystal structures are limited to thin films, while the investigation on single-particle magnetism of FePt intermetallics is few [17][18][19][20][21][22]. Liu et al [23] first reported a systemic study on FePt intermetallic NPs prepared by a sol-gel method.…”

On the tetragonality of martensites in ferrous shape memory alloy Fe3Pt: A first-principles study

“…Nevertheless, one should also note that the L1 2 phase is not the 0 K ground state of Fe 3 Pt. Barabash [42] and previous theoretical values (GGA (DTU) [43] and GGA (CMU) [44]). Results computed with the 2 Â 2 Â 2 and 3 Â 3 Â 3 supercells (SC) are given by squares and triangles, respectively.…”

Determination of enthalpies (‘Heats’) of formation

“…Differential scanning calorimetry (DSC) is widely used in the study of thermal protein denaturation 9. Wang et al34 have reported DSC studies that provided enthalpies of formation of Fe 3 Pt, FePt, and FePt 3 in ordered intermetallic multilayer Fe/Pt films important in magnetic recording media. Stevens et al35 have used the nonclassical method of threshold photoelectron photoion coincidence to determine the enthalpies of formation of the unstable species phenyl, phenylium and of nitrosobenzene and nitrosobenzene ions with ATcT analysis 24…”