Pressure-Induced Invar Behavior inPd3Fe

Abstract

Synchrotron x-ray diffraction (XRD) measurements, nuclear forward scattering (NFS) measurements, and density functional theory (DFT) calculations were performed on L1_{2}-ordered Pd3Fe. Measurements were performed at 300 K at pressures up to 33 GPa, and at 7 GPa at temperatures up to 650 K. The NFS revealed a collapse of the 57Fe magnetic moment between 8.9 and 12.3 GPa at 300 K, coinciding with a transition in bulk modulus found by XRD. Heating the sample under a pressure of 7 GPa showed negligible thermal expansion from 300 to 523 K, demonstrating Invar behavior. Zero-temperature DFT calculations identified a ferromagnetic ground state and showed several antiferromagnetic states had comparable energies at pressures above 20 GPa.

Dynamics of iron atoms across the pressure-induced Invar transition in Pd3Fe

“…In the present measurements, the transition occurred at higher pressures than reported previously in ref. [14], which showed diminished quantum beats at 12.3 GPa, and only weak beats were visible at pressures of 15.1 GPa or higher. The difference between the two sets of measurements is not caused by differences in the chemical compositions of the samples, which came from the same homogenized ingot.…”

“…The preparation of Pd 3 57 Fe by the arc-melting and homogenization of a small ingot was described previously [14]. A Merrill-Bassett, Tel-Aviv-type diamond anvil cell (DAC) [15] was used to generate pressure on the sample.…”

“…Pressure has long been used in studies of Invar materials [8][9][10][11][12], but recently a new phenomenon was discovered at high pressures in Fe-Ni alloys away from the classical Invar composition [13] [14]. Under a pressure of 7 GPa the alloy Pd 3 Fe exhibits negligible thermal expansion from 300 K to approximately 523 K. The same study showed that the volume collapse at pressures from 10 to 15 GPa was accompanied by a magnetic transition from the ferromagnetic (FM) ground state to a low-spin (LS) state.…”

Stress-induced large Curie temperature enhancement inFe64Ni36Invar alloy

“…3,16 Therefore, this effective temperature invariant thermal expansion can be exploited in a number of technological applications such as precision measurements for standards, large size cryogenic liquid containers, etc. 15,17 Furthermore, the Invar effect is not limited to being a property of only Fe-Ni alloys, but it is also found in many other crystalline three dimensional ͑3D͒ systems such as Fe-Pt, Pd 3 Fe, Fe 3 C, or Fe-Cu, [18][19][20][21][22] amorphous Fe alloys, [23][24][25] as well as intermetallic systems such as R-Fe ͑R = Rare Earth͒. 26,27 Hence, these alloys can be structurally ordered or disordered, ferromagnetic or antiferromagnetic.…”

High pressure neutron and X-ray diffraction at low temperatures

“…Such behaviour is known as 'Invar-like', as it was originally observed in the FeNi 36 alloy, Invar. Although their are reported observations of this behaviour in other Fe alloys [99], it tends to be realised in non-ambient phases, and rarely in materials with the required beam transparency and mechanical properties for high pressure diffraction apparatus. Fe-Ni compounds tend to be magnetic, brittle at low temperatures, and highly scattering of both neutrons and X-rays, making them far from ideal for pressure cell design.…”