Binary FePt Research Articles

Novel Rare Earth (RE)-Free Nanocomposite Magnets Derived from L10-Phase Systems.

In the quest for novel rare earth (RE)-free magnetic materials, which also exhibit other additional properties such as good corrosion resistance and potential to operate at higher temperatures, an alloy deriving from the binary FePt system, with Mo and B addition, has been synthesized for the first time, using the out-of-equilibrium method of rapid solidification form the melt. The alloy with the composition Fe49Pt26Mo2B23 has been subjected to thermal analysis through differential scanning calorimetry in order to detect the structural disorder - order phase transformation as well as to study the crystallization processes. For the stabilization of the formed hard magnetic phase, the sample has been annealed at 600 °C and further structurally and magnetically characterized by means of X-ray diffraction, transmission electron microscopy, 57Fe Mössbauer spectrometry as well as magnetometry experiments. It has been proven that after annealing at 600 °C the tetragonal hard magnetic L10 phase emerges via crystallization from a disordered cubic precursor and becomes the predominant phase in terms of relative abundance. Moreover, it has been revealed by quantitative analysis via Mössbauer spectroscopy that the annealed sample exhibits a complex phase structure, where the L10 hard magnetic phase is accompanied by few other soft magnetic phases, in minority abundance: the cubic A1, orthorhombic Fe2B and residual intergranular region. The magnetic parameters have been derived from 300 K hysteresis loops. It was shown that, contrary to the as-cast sample which behaves as a typical soft magnet, the annealed sample presents strong coercivity and high remanent magnetization, accompanied by a large saturation magnetization. These findings offers good insight into the potential developing of novel class of RE-free permanent magnets, based on Fe-Pt-Mo-B, where the magnetic performance emerges from the co-existence of hard and soft magnetic phases in controlled and tunable proportions, capable of finding good applicability in fields requiring good catalytic properties and strong corrosion resistance.

HAMR switching dynamics and the magnetic recording quadrilemma

We investigate the dynamical switching process of Heat Assisted Magnetic Recording (HAMR) by numerical calculations of switching probability using an atomistic model. Calculations show that at the elevated write temperature of HAMR there is a loss of information arising from ’backswitching’: a thermodynamic phenomenon which comes into play when the ratio of the Zeeman energy to the thermal energy is insufficiently large to completely stabilise the switched direction. We consider the special case of Heated Dot Magnetic Recording, where a reduction of switching probability can be related to a bit error rate. We show that the backswitching becomes more pronounced at faster write times. Also, we show that in the case of current recording media, based on the binary alloy FePt, backswitching will be a more stringent limitation on recording density than the usually assumed thermal stability criterion.

Segregation tendency and properties of FeRh1-xPtx alloys

In this work, the phase stability and properties of FeRh1-xPtx alloys (x = 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875, 1) are studied within the framework of the density functional theory implemented in the VASP software package. It is found that the antiferromagnetic spin configurations AFM-II and AFM-III are energetically favorable for FeRh1-xPtx with a Pt content in the range of 0 < x ≤ 0.625 and 0.625 < x < 1, correspondingly. While, binary FePt alloy is ordered ferromagnetically. It is shown that compounds with 0 < x ≤ 0.625 are found to be stable with respect to decomposition into stable binary FeRh and FePt compounds at zero and finite temperatures. In the case of compositions with x = 0.75 and 0.875, their stability against segregation is predicted at finite temperatures. An increase in temperature enhances the stabilization of FeRh1-xPtx with respect to decomposition into two-component mixture.

Magnetic Phase Coexistence and Hard-Soft Exchange Coupling in FePt Nanocomposite Magnets.

With the aim of demonstrating phase coexistence of two magnetic phases in an intermediate annealing regime and obtaining highly coercive FePt nanocomposite magnets, two alloys of slightly off-equiatomic composition of a binary Fe-Pt system were prepared by dynamic rotation switching and ball milling. The alloys, with a composition Fe53Pt47 and Fe55Pt45, were subsequently annealed at 400 °C and 550 °C and structurally and magnetically characterized by means of X-ray diffraction, 57Fe Mössbauer spectrometry and Superconducting Quantum Interference Device (SQUID) magnetometry measurements. Gradual disorder–order phase transformation and temperature-dependent evolution of the phase structure were monitored using X-ray diffraction of synchrotron radiation. It was shown that for annealing temperatures as low as 400 °C, a predominant, highly ordered L10 phase is formed in both alloys, coexisting with a cubic L12 soft magnetic FePt phase. The coexistence of the two phases is evidenced through all the investigating techniques that we employed. SQUID magnetometry hysteresis loops of samples annealed at 400 °C exhibit inflection points that witness the coexistence of the soft and hard magnetic phases and high values of coercivity and remanence are obtained. For the samples annealed at 500 °C, the hysteresis loops are continuous, without inflection points, witnessing complete exchange coupling of the hard and soft magnetic phases and further enhancement of the coercive field. Maximum energy products comparable with values of current permanent magnets are found for both samples for annealing temperatures as low as 500 °C. These findings demonstrate an interesting method to obtain rare earth-free permanent nanocomposite magnets with hard–soft exchange-coupled magnetic phases.

Mn-Induced Thermal Stability of L10 Phase in Fept Magnetic Nanoscale Ribbons.

Magnetic nanoscale materials exhibiting the L10 tetragonal phase such as FePt or ternary alloys derived from FePt show most promising magnetic properties as a novel class of rare earth free permanent magnets with high operating temperature. A granular alloy derived from binary FePt with low Pt content and the addition of Mn with the nominal composition Fe57Mn8Pt35 has been synthesized in the shape of melt-spun ribbons and subsequently annealed at 600 °C and 700 °C for promoting the formation of single phase, L10 tetragonal, hard magnetic phase. Proton-induced X-ray emission spectroscopy PIXE has been utilized for checking the compositional effect of Mn addition. Structural properties were analyzed using X-ray diffraction and diffractograms were analyzed using full profile Rietveld-type analysis with MAUD (Materials Analysis Using Diffraction) software. By using temperature-dependent synchrotron X-ray diffraction, the disorder–order phase transformation and the stability of the hard magnetic L10 phase were monitored over a large temperature range (50–800 °C). A large interval of structural stability of the L10 phase was observed and this stability was interpreted in terms of higher ordering of the L10 phase promoted by the Mn addition. It was moreover found that both crystal growth and unit cell expansion are inhibited, up to the highest temperature investigated (800 °C), proving thus that the Mn addition stabilizes the formed L10 structure further. Magnetic hysteresis loops confirmed structural data, revealing a strong coercive field for a sample wherein single phase, hard, magnetic tetragonal L10 exists. These findings open good perspectives for use as nanocomposite, rare earth free magnets, working in extreme operation conditions.

Structural, electronic and magnetic properties of the ordered binary FePt, MnPt, and CrPt3 alloys

We perform ab initio simulations to investigate the structural, electronic and magnetic properties of the ordered binary FePt, MnPt, and CrPt3 alloys. In particular, equilibrium structural lattice parameters, electronic properties such as density of states (DOS), partial density of states (PDOS) and electronic band structure of each binary alloys are investigated and interpreted. Moreover, the magneto-crystalline anisotropy energies (MAE) are calculated. We found MAE values of FePt, MnPt and CrPt3 ordered alloys to be 2.66, 0.46 and 0.42 meV/f.u., respectively, corresponding to magneto-crystalline anisotropy constant K of 7.6 × 107, 1.3 × 107 and 1.1 × 107 erg/cm3, respectively. The large MAE and K values reveal that FePt, MnPt and CrPt3 binary alloys are eligible to be key components in magneto-optical and opto-electronic devices. In addition, we estimated the Curie temperatures of the three ordered alloys from exchange energy. We found the TC of L10-FePt, L10-MnPt and L12 CrPt3 to be 955 K, 989 K and 762 K, respectively. The high Curie temperatures obtained enable the ordered alloys to serve as write assist in Heat-Assisted Magnetic Recording (HAMR). We believe that our findings would pave the way to fabricate bulk and thin films based on the ordered binary FePt, MnPt, and CrPt3 ordered alloys that have attractive electronic and magnetic properties.

Effect of Mn addition on the thermal stability and magnetic properties of rapidly-quenched L10 FePt alloys

Nano-composite magnets with L10 structure derived from binary FePt alloys and prepared as melt-spun ribbons are of current interest due to their higher operating temperature and the ability to be cast as a two-phase magnet with exchange spring magnetic properties, as both soft and hard magnetic phase may emerge from the same metastable precursor, i.e. the disordered cubic A1 phase. The present paper studies the effect of Mn addition on the thermal stability and phase structure, on the abundance of the hard magnetic phase and relative proportion of the soft ones, on the microstructure of the alloy as a function of temperature and on the overall magnetic properties. The interplay of the various magnetic sublattices in the ordering of the L10 phases as a consequence of introducing antiferromagnetically coupled Mn atoms in the alloy composition is discussed and interpreted in terms of microstructural changes induced by this addition as revealed by high resolution transmission electron microscopy and X-ray diffraction. The temperature evolution of the phase composition and structural parameters is monitored using synchrotron radiation powder diffraction, while the compositional aspects are investigated using proton-induced X-ray emission and energy dispersive X-ray spectroscopy. Magnetic measurements reveal the magnetic parameters of interest (coercivity, remanence, Curie temperature, saturation magnetization), as well as the exchange-coupled two-phase nature of these magnets and provide information that hints at possible spin reorientation transitions in the Mn-containing planes of the L10 superlattice.

Simple Replacement Reaction for the Preparation of Ternary Fe1–xPtRux Nanocrystals with Superior Catalytic Activity in Methanol Oxidation Reaction

The finding of new metal alloyed nanocrystals (NCs) with high catalytic activity and low cost to replace PtRu NCs is a critical step toward the commercialization of fuel cells. In this work, a simple cation replacement reaction was utilized to synthesize a new type of ternary Fe(1-x)PtRu(x) NCs from binary FePt NCs. The detailed structural transformation from binary FePt NCs to ternary Fe(1-x)PtRu(x) NCs was analyzed by X-ray absorption spectroscopy (XAS). Ternary Fe(35)Pt(40)Ru(25), Fe(31)Pt(40)Ru(29), and Fe(17)Pt(40)Ru(43) NCs exhibit superior catalytic ability to withstand CO poisoning in methanol oxidation reaction (MOR) than do binary NCs (FePt and J-M PtRu). Also, the Fe(31)Pt(40)Ru(29) NCs had the highest alloying extent and the lowest onset potential among the ternary NCs. Furthermore, the origin for the superior CO resistance of ternary Fe(1-x)PtRu(x) NCs was investigated by determining the adsorption energy of CO on the NCs' surfaces and the charge transfer from Fe/Ru to Pt using a simulation based on density functional theory. The simulation results suggested that by introducing a new metal into binary PtRu/PtFe NCs, the anti-CO poisoning ability of ternary Fe(1-x)PtRu(x) NCs was greatly enhanced because the bonding of CO-Pt on the NCs' surface was weakened. Overall, our experimental and simulation results have indicated a simple route for the discovery of new metal alloyed catalysts with superior anti-CO poisoning ability and low usage of Pt and Ru for fuel cell applications.

The impact of deposition temperature on L1 formation in FePt films

Binary FePt films with compositions in the range of 42.4 to 54.0 at. % Pt were sputter deposited at temperatures between 100 and 300 °C. Films deposited at 250 and 300 °C were fully L10 ordered, whereas films deposited between 100 and 200 °C were either A1 or a mixture of A1 and L10. Differential scanning calorimetry studies following deposition showed a bifurcation in the post-deposition formation characteristics of the L10 phase for films deposited between 100 and 200 °C depending on film composition. For films with compositions &amp;gt;47 at. % Pt, L10 formation kinetics were identical to those for room-temperature deposited films. In contrast, for films with &amp;lt;47 at. % Pt, significantly higher temperatures were needed for full transformation to the L10 phase. Thus the choice of deposition temperature and film composition is critical to achieving fully L10 films during deposition. The Curie temperature of the L10 phase was not impacted by the deposition temperature.

Formation of Highly Ordered Alloy Nanoparticles Based on Precursor-Filled Latex Spheres

An experimental approach is presented, allowing the preparation of substrate supported, hexagonally arranged metallic alloy nanoparticles with narrow size distributions, well-defined interparticle distances, and controlled chemical composition. The method is based on miniemulsion polymerization and isotropic plasma etching. Polystyrene (PS) and poly(methyl methacrylate) (PMMA) colloids—in the present study containing Fe- and Pt-precursor complexes in a predefined ratio—are deposited onto hydrophilic Si/SiO2 substrates by dip-coating, forming a highly ordered monolayer. Contrary to colloidal lithography, here, precursor-filled polystyrene colloids serve as carriers for the alloy forming elements. After reactive ion etching and annealing, hexagonally ordered arrays of crystalline FePt nanoparticles are formed exhibiting the desired 1:1 Fe–Pt ratio, as revealed by detailed analysis after each preparation step. Formation of stoichiometric binary alloy FePt nanoparticles is confirmed by determining magnetic hy...

Re-evaluation of the impact of ternary additions of Ni and Cu on the A1 to L1 transformation in FePt films

The impact of ternary additions of Ni (1.6–21.5 at. %) and Cu (1.3–17.3 at. %) on the A1 (face centered cubic, fcc) to L10 phase transformation in FePt films has been re-evaluated based on compositions obtained using energy dispersive x-ray spectrometry (EDS). The data presented here serve as corrections to results reported in six previous studies [D. C. Berry and K. Barmak, J. Appl. Phys. 102, 024912 (2007); 101, 014905 (2007); 99, 08G901 (2006); D. C. Berry, J. Kim, K. Barmak, K. Wierman, E. B. Svedberg, and J. K. Howard, Scr. Mater. 53, 423 (2005); K. Barmak, J. Kim, D. C. Berry, W. N. Hanani, K. Wierman, E. B. Svedberg, and J. K. Howard, J. Appl. Phys. 97, 024902 (2005); K. Barmak, J. Kim, D. C. Berry, K. W. Wierman, E. B. Svedberg, and J. K. Howard, ibid. 95, 7486 (2004)]. The new EDS compositions do not change the following conclusions of these previous studies: (i) when ternary FeNiPt and FeCuPt alloys are compared with binary FePt alloys with the same Pt content, it is seen that additions of Ni slow the transformation kinetics, whereas additions of Cu have no measurable impact on the kinetics, (ii) the Curie temperature of the L10 phase is lowered by additions of Ni or Cu, (iii) the Curie temperature of the A1 phase is increased by additions of Ni, but lowered by additions of Cu, and (iv) the transformation enthalpy is lowered by large additions of Ni, but is unaffected by additions of Cu. The ordering behavior of FeCuPt alloys as evidenced by the kinetic ordering temperature is compared with other reports in the literature based on magnetic measurements.

The A1 to L1 transformation in FePt films with ternary alloying additions of Mg, V, Mn, and B

The impact of ternary additions of Mg, V, Mn, and B on the A1 [face centered cubic (fcc)] to L10 phase transformation has been studied. The films were cosputter deposited from elemental targets at room temperature and annealed after deposition. The films had Mg additions in the range ∼0–2.6 at.%, V additions in the range 0.7–12.2 at.%, Mn additions in the range 2.2–16.3 at.%, and B additions in the range 1.2–12.9 at.%. For all four ternary alloy systems, annealing resulted in the formation of no other phases than the L10 phase. Ternary additions of &amp;lt;1.8 at.% Mg, &amp;lt;5.8 at.% V, &amp;lt;6.0 at.% Mn, and &amp;lt;4.8 at.% B had little or no impact on the kinetic ordering temperature (KOT). The behavior of the activation energy for the transformation mirrored that for the KOT, except for Mg additions, which showed no measurable impact for the compositions studied. The transformation enthalpies for the ternary alloys were similar to those for binary FePt films. Only four of the films (with additions of 2.6 at.% Mg, 2.2 at.% and 6.0 at.% Mn, and 4.8 at.% B) for which the Curie transition was observed had lower TC than the binary FePt films with the same Pt content.

A1 to L1$_{0}$ Transformation in FePt Films With Ternary Alloying Additions of Ag and Au

The formation of the ordered L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> phase from the parent A1 (face centered cubic, fcc) solid solution phase in ternary FeAgPt (1.5-16.7 at.% Ag) and FeAuPt (1.9-13.8 at.% Au) films has been studied. The films were co-sputter deposited from elemental targets at room temperature and annealed after deposition. The annealed films showed the presence of fcc Ag peaks for concentrations of 6.9 at.% Ag and higher and fcc Au diffraction peaks for concentration of 7.2 at.% Au and higher. Therefore, these two elements are not fully soluble in L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> FePt. The kinetic ordering temperature is higher in both types of ternary films when compared with binary FePt. However, the activation energy for ordering is higher only for high concentrations of Au. The enthalpy for decomposition of FeAgPt and FeAuPt into L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> FePt and Ag or Au is not measurably different than that for transformation of the A1 phase to the L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> phase in binary FePt. Ternary additions of Ag and Au have no impact on the Curie temperature of the L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> phase.

Bifunctional Magneto-Optical FePt−CdS Hybrid Nanoparticles

This paper describes preparation of binary FePt−CdS hybrid nanoparticles by spontaneous heteroepitaxial nucleation and growth of the CdS component onto FePt-seed nanoparticles in high-temperature organic solution. FePt nanoparticles with average sizes of 4 and 9 nm were used as seeds. Lattice mismatch makes complete coating of the seed particles unfavorable, resulting in peanut-like and flower-like FePt−CdS nanoparticles. The CdS photoluminescence is quenched in 9 nm FePt−CdS hybrid nanoparticles. The band edge emission is observed in 4 nm FePt−CdS nanoparticles, albeit with substantially lower intensity than in pure CdS nanoparticles. We suggest that the strong FePt-size dependent photoluminescence intensity results from the interplay between interface charge transfer and quantum confinement effects.

Comparative study on thermal and plasma enhanced CVD grown carbon nanotubes from gas phase prepared elemental and binary catalyst particles

AbstractThe preparation of nanoparticles in the gas phase through inert gas condensation is a very versatile method to fabricate catalyst particles that act as catalytic templates for carbon nanotube synthesis since the method allows for easy control of the catalysts' elemental composition and their morphology. In this contribution we report on the synthesis of carbon nanotubes via two distinct chemical vapour deposition routes, thermal and plasma enhanced chemical vapour deposition, using such gas phase prepared elemental Fe catalyst particles as well as binary FePt nanoparticles. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Microstructural and magnetic studies of L1 0 FePt–SiO 2 nano-composite thin film with columnar structure for perpendicular magnetic recording

(Fe 50Pt 50) 100− x -(SiO 2) x films ( x=0–30 vol%) were grown on a textured Pt(0 0 1)/CrRu(0 0 2) bilayer at 420 °C using glass substrates. FePt(0 0 1) preferred orientation was obtained in the films. Interconnected microstructure with an average grain size of about 30 nm is observed in the binary FePt film. As SiO 2 is incorporated, it precipitates as particles are dispersed at FePt grain boundaries. When the content of SiO 2 is increased to 13 vol%, columnar FePt with (0 0 1) texture separated by SiO 2 is attained. The FePt columns have a length/radius ratio of 2:1. Additionally, the mean grain size is reduced to about 13 nm. The development of this well-isolated columnar structure leads to an enhancement in coercivity by about 44% from 210 to 315 kA/m. As the SiO 2 content exceeds 20 vol%, a significant ordering reduction is found accompanied by a transformation of preferred orientation from (0 0 1) to (2 0 0) and the columnar structure disappears, resulting in a drastic degradation in magnetism. The results of our study suggest that isolated columnar, grain refined, (0 0 1)-textured FePt film can be achieved via the fine control of SiO 2 content. This may provide useful information for the design of FePt perpendicular recording media.

Effect of alloy composition on the thermodynamic and kinetic parameters of the A1 to L1 transformation in FePt, FeNiPt, and FeCuPt films

Differential scanning calorimetry is used to investigate the A1 to L10 ordering transformation in binary FePt films with compositions in the range of 39.3−55.3 at. % Pt and ternary FePt-based films with additions of Cu up to 20 at. % and Ni up to 25 at. % for a range of Fe/Pt ratios. For FePt and FeCuPt, these are extensions of previously studied ranges [K. Barmak, J. Kim, D. C. Berry, W. N. Hanani, K. Wierman, E. B. Svedberg, and J. K. Howard, J. Appl. Phys. 97, 024902 (2005); D. C. Berry, J. Kim, K. Barmak, K. Wierman, E. B. Svedberg, and J. K. Howard, Scr. Mater. 53, 423 (2005)]. Parameters including the A1 and L10 phase Curie temperatures, the kinetic ordering temperature, the activation energy, and the transformation enthalpy are reported. For FePt, the L10 Curie temperature reaches a maximum of 457 °C near 45 at. % Pt. In contrast, the A1 Curie temperature has an essentially constant value of 300 °C across the full composition. Both the kinetic ordering temperature and activation energy show a minimum near 46 at. % Pt, while the magnitude of the transformation enthalpy has its maximum near 50 at. % Pt. Ni additions to FePt in general lower the L10 Curie temperature, but they increase the A1 Curie temperature. The kinetic ordering temperature and the activation energy increase for all Ni additions, whereas the transformation enthalpy decreases measurably only for Ni additions over ∼10 at. %. Cu additions to FePt act as magnetic diluents regarding both the A1 and L10 phase Curie temperatures, with increased Cu content resulting in decreased Curie temperature. Conversely, Cu additions have no significant effect on the kinetic ordering temperature, activation energy, or transformation enthalpy when compared to equivalent binary alloys. The relevance of our findings to alloy development for ultrahigh density magnetic recording media is discussed, with specific focus on the potential for heat-assisted magnetic recording.

Coercivity enhancement of melt spun FePt ribbons by Au addition

The effect of Au content on the magnetic properties and microstructure of melt spun (FePt)100−xAux (x=0–40) ribbons have been investigated. X-ray diffraction and thermal magnetic analysis results indicate that Au-rich phase coexists with ordered L10-FePt(Au) phase in ternary FePtAu ribbons after an isothermal annealing. Meanwhile, the Curie temperature of L10-FePt(Au) phase in annealed (FePt)100−xAux (x=0–40) ribbons is almost unchanged, revealing that higher volume fraction of Au addition does not modify the composition of the L10-FePt(Au) phase. All the Au containing ribbons exhibit a completely isolated L10-FePt(Au) granular structure, and the grain size is effectively decreased with the increase of Au content. As a result, the intrinsic coercivity (Hci) of the ribbons increases substantially from 2.1kOe for binary FePt to 19.5kOe for (FePt)60Au40.

Effect of Fe/Pt ratio on the magnetic properties and corrosion behavior of nanocomposite FePtB ribbons

(Fe 1− y Pt y ) 82B 18 ( y=0.5–0.7) alloys were adopted to study the effect of Fe/Pt ratio on the magnetic properties and phase evolution of FePtB-type nanocomposite melt spun ribbons. In addition, the differences in magnetic properties and corrosion behavior between binary FePt and ternary FePtB ribbons were also investigated. An i H c of more than 12 kOe has been obtained in (Fe 0.6Pt 0.4) 82B 18, while B r of 8.9 kG, i H c of 8.2 kOe and ( BH) max of 13.2 MGOe are achieved in (Fe 0.675Pt 0.325) 82B 18. Increasing Fe/Pt ratio was found to change the type of ferrous borides and their volume fraction, which enhanced the exchange-coupling effect between ferrous borides and magnetically hard γ 1-FePt phase, and the magnetic properties drastically. Although FePtB ribbons exhibit superior magnetic performance compares to that of FePt, they are susceptible to corrosion due to the existence of Fe–B phases in the ribbons.

Recent Advances in Chemical Synthesis, Self‐Assembly, and Applications of FePt Nanoparticles

AbstractThis paper reviews recent advances in chemical synthesis, self‐assembly, and potential applications of monodisperse binary FePt nanoparticles. After a brief introduction to nanomagnetism and conventional processes of fabricating FePt nanoparticles, the paper focuses on recent developments in solution‐phase syntheses of monodisperse FePt nanoparticles and their self‐assembly into nanoparticle superlattices. The paper further outlines the surface, structural, and magnetic properties of the FePt nanoparticles and gives examples of three potential applications in data storage, permanent magnetic nanocomposites, and biomedicine.