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Exchange integrals for f.c.c. Fe–Pt alloys in the whole platinum content range are estimated. Temperature dependences of spontaneous magnetizations of Fe and Pt subsystems for various platinum contents are obtained.
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The diffusion kinetics in a CoCrFeMnNi high entropy alloy is investigated by a combined radiotracer-interdiffusion experiment applied to a pseudo-Ni 15 couple. As a result, the composition-dependent tracer diffusion coefficients of Co, Cr, Fe and Mn are determined. The elements are characterized by significantly different diffusion rates, with Mn b...
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... As a comparison, the magnetic structure of the L1 2 super-structure of Fe 25 Pt 75 is unclear. 26 The theory predicts that l Fe ¼ 3.25 l B and l Pt ¼ 0.38 l B for L1 2 Fe 25 Pt 75 , 26 i.e., l à Fe ¼ 4.39 l B , assuming ferromagnetic ordering. Therefore, the moment values of A1 and L1 2 Fe 25 Pt 75 are comparable, with the latter about 18% larger. ...
... As a comparison, the magnetic structure of the L1 2 super-structure of Fe 25 Pt 75 is unclear. 26 The theory predicts that l Fe ¼ 3.25 l B and l Pt ¼ 0.38 l B for L1 2 Fe 25 Pt 75 , 26 i.e., l à Fe ¼ 4.39 l B , assuming ferromagnetic ordering. Therefore, the moment values of A1 and L1 2 Fe 25 Pt 75 are comparable, with the latter about 18% larger. ...
... Furthermore, our A1 Fe 29 Pt 71 thin film is ferromagnetic at room temperature, whereas the L1 2 Fe 25 Pt 75 is likely ferrimagnetic, if not antiferromagnetic. 26 As the Fe concentration increases, l à Fe reaches a peak value of 3.6 l B for Fe 35 Pt 65 . A simple moment mixing argument would yield l à Fe of 3.3 l B and a monotonically decreasing l à Fe with the Fe concentration. ...
We systematically study the magnetic properties, electron transport, and the anomalous Hall effect
(AHE) in FexPt100-x solids over a wide composition range. These solids are characterized by strong
spin-orbit interaction and enhanced magnetic moments from both elements. In our study, we vary
the thickness and the composition of the thin films, the temperature of measurement, and the magnitude
of the magnetic field in various directions. We have determined the Hall angle, the spin diffusion
length, and the electron mean free path in this alloy system. The AHE is more than 3 orders
of magnitude larger than the normal Hall effect, making FexPt100-x a good candidate for spintronic
applications. The Hall angle determined in the FexPt100-x solids is comparable to that in pure Pt.
From the analysis on the correlation between the AHE and electron transport, we find that the AHE
is dominated by both the intrinsic Karplus-Luttinger (Berry phase) mechanism and the extrinsic
side-jump mechanism.
... The details of computational model are described in Ponomarova et al. (2014), Tatarenko and Bokoch (2008). ...
... For L1 2 -type of (super)structure, these parameters were determined in Ponomarova et al. (2014). ...
... Analysis of theoretical and experimental values of the Fe and Pt magnetic moments per atom in Fe-Pt alloys with different Pt contents provided in Ponomarova et al. (2014) shows that s Fe = 3/2 and s Pt = 1/ 2 seem to be the most appropriate spin numbers for Fe-Pt alloys. ...
The objective of this study is to calculate the parameters of strong exchange interactions within magnetic nanoparticles and weak (dipolar + anisotropic) interactions for the patterns of nanoparticles injected into non-magnetic substrate. The Fe–Pt magnetic system was chosen as the best applicable for this purpose. However, computations done in this work may be extended to the other f.c.c. magnetic systems. In this paper, we estimated the parameters of exchange interactions within the magnetic Fe–Pt nanoparticles close to equiatomic composition with 4–10 nm in diameter. Size effect for exchange interaction parameters was found. Temperature dependences of spontaneous magnetizations for Fe and Pt subsystems of nanoparticles with different sizes at fixed equiatomic composition were obtained. Total magnetic energies of weak interactions between Fe and Pt nanoparticles injected different matrixes were also estimated. Magnetic moment ordering temperature was evaluated within the simple model for ordered and disordered Fe–Pt nanoparticles of various sizes (4–10 nm) separated by different interparticle distances (30–50 nm).
... Moreover, both bulk Fe-rich and Pt-rich FePt alloys exhibit noteworthy magnetic properties. In the first case, Fe x Pt 100-x (x > 78) alloys display a first-order phase transition from disordered fcc phase to ordered a phase during cooling and a reverse process on heating and magnetic fields induce a phase transition from the fcc phase to the a phase near the transition temperature [5]; in addition, the Fe 3 Pt phase is a good Invar alloy showing a low coefficient of thermal expansion [6]. In the second case, the chemically ordered phase L1 2 FePt 3 is antiferromagnetic below 170 K displaying two different spin alignment planes [7]. ...
We present new models for the activity of iron (γFe) in solid face-centered cubic (fcc) and liquid FePt alloy at high temperature and pressure to facilitate their use as sliding buffer redox sensors under extreme conditions. Numerous experimental studies of γFe in FePt alloy at 100 kPa have produced a wide spread of values. By favoring high-temperature studies that are more likely to have produced equilibrium measurement and excluding experiments for compositions and temperatures that probably encountered ordered or unmixed low-temperature phases, we regress an asymmetric Margules activity–composition model with parameters WFePtfcc=-121.5±2.1 kJ mol−1 and WPtFefcc=-93.3±4.3 kJ mol−1. These values are close to the widely used model of Kessel et al. (2001), but for Pt-rich compositions they predict larger Fe activities and correspondingly more reduced oxygen fugacities. Activity–composition relations in liquid FePt are calibrated from direct measurements of activities and, most sensitively, from the trace of the Fe–Pt liquidus. Together, these yield asymmetric Margules parameters of WFePtliq=-124.5 kJ mol−1 and WPtFeliq=-94.0 kJ mol−1. The effects of pressure on both fcc and liquid FePt alloy are considered from excess-volume relations. Both solid and liquid alloy display significant positive excess volumes of mixing. Extraction of the excess volume of mixing for fcc FePt alloy requires filtering data for ordered low-temperature phases and corrections for the effects of magnetostriction on Fe-rich compositions which exhibit “Invar” behavior. Applied at high temperatures and pressures, both solid and liquid FePt alloys have strongly negative deviations from ideality at low pressure, which become closer to ideal at high pressure. These models provide a provisional basis for the calculation of aFe in high-temperature, high-pressure experiments that, when combined with estimates of aFeO, allow characterization of fO2 under conditions relevant to magma oceans, core formation, and differentiation processes in the lower mantle of Earth or on other terrestrial planets. Improvements in these models require new constraints on the equation of state of FePt fcc alloy and documentation of the high-pressure melting relations in the system Fe–Pt.
The aim of this research is to calculate the exchange coupling constants within binary magnetic nanoparticles. An Fe–Pd magnetic system with nanoparticles in range of 5–50 nm in diameter is chosen for this purpose since it undergoes different phase transitions and its magnetic properties vary under external influences. Atomic ordering and external pressure influences are investigated for Fe–Pd compounds of different compositions.
