Magnetic Data Storage Applications Research Articles

Enhancing the spin–orbit torque efficiency in Pt/CoFeB/Pt based perpendicularly magnetized system

In the recent past, current-induced magnetization reversal (CIMR) has been extensively studied on the heterostructures prepared with heavy metal (HM) and ferromagnet (FM) having spin–orbit torque (SOT). The critical current density (Jc) for magnetization switching depends on the SOT efficiency. In this study, we have chosen Ta/Pt/CoFeB/Pt/Ta/CoFeB/Pt heterostructure having perpendicular magnetic anisotropy (PMA) with broken lateral symmetry and an in-plane magnetized (IMA) ferromagnetic layer on top of the Ta layer. In this heterostructure, we have utilized the SOT originated by the spin-Hall effect that arises from two materials having opposite spin Hall angles i.e. the bottom Pt and the top Ta layer. We have also introduced lateral space inversion asymmetry (SIA) that combines both damping-like and field-like field. The enhanced spin Hall angle, the stray field by IMA ferromagnetic layer, and the lateral SIA effect jointly enhances the SOT efficiency of the system to reduce the Jc for CIMR. We have found that the SOT efficiency and the effective spin Hall angle of our newly designed heterostructure to be 106 Oe/1011A/m2 and 0.23, respectively. Thus we have achieved CIMR with a lower critical current density of 8.65×1010 A/m2 and 3.35×1010 A/m2 at 0 Oe and 600 Oe field applied in-plane (IP), respectively. Due to the lower Jc for CIMR our newly designed heterostructure has potential in low-power magnetic data storage applications.

First observation on emergence of strong room-temperature ferroelectricity and multiferroicity in 2D-Ti3C2T x free-standing MXene film.

Two-dimensional (2D) multiferroics are key candidate materials towards advancement of smart technology. Here, we employed a simple synthesis approach to address the long-awaited dream of developing ferroelectric and multiferroic 2D materials, especially in the new class of materials called MXenes. The etched Ti3C2Tx MXene was first synthesized after HF-treatment followed by a delamination process for successful synthesis of free-standing Ti3C2Tx film. The free-standing film was then exposed to air at room-temperature and heated at different temperatures to form a TiO2 layer derived from the Ti3C2Tx MXene itself. The ferroelectric measurement showed a clear polarization hysteresis loop at room-temperature. Also, due to the reported ferromagnetic behavior of Ti3C2Tx MXene, our composite could show multiferroic properties at room-temperature. The magnetoelectric coupling test was also performed that showed a clear, switchable spontaneous polarization under applied magnetic field. TiO2 is reported to be an incipient ferroelectric that assumes a ferroelectric phase in composite form. The structural and morphological analysis confirmed successful synthesis of free-standing film and the Raman spectroscopy revealed the formation of different phases of TiO2 and the observed ferroelectricity could be due to structural deformation as a result of the formation of this new phase. The measured value of remanent polarization is 0.5 μC cm−2. This is the first report on the existence of a ferroelectric phase and multiferroic coupling in 2D free-standing MXene film at room-temperature which opens-up the possibility of 2D material-based electric and magnetic data storage applications at room-temperature.

A Review of Hexagonal and Spinel Ferrites for Data Storage Applications

The scientific community is giving considerable attention to making a wider hysteresis loop required for miniaturization of the magnetic devices for improving data storage capability. In this context, a review including the present state of the art of the hexagonal ferrites (HFs) and spinel ferrites (SFs) used for the data storage applications is reported. A classification scheme of ferrites useful for data storage is suggested, the magnetic properties and synthesis methods of ferrites are reviewed. A few X-ray diffraction (XRD) and vibration sample magnetometer (VSM) results on ferrites from the literature are discussed. Further, the possible directions for improving the capability of ferrites for magnetic data storage applications are reported. This review should provide a faster understanding of this area.

Spray-Deposited Anisotropic Ferromagnetic Hybrid Polymer Films of PS-b-PMMA and Strontium Hexaferrite Magnetic Nanoplatelets.

Spray deposition is a scalable and cost-effective technique for the fabrication of magnetic hybrid films containing diblock copolymers (DBCs) and magnetic nanoparticles. However, it is challenging to obtain spray-deposited anisotropic magnetic hybrid films without using external magnetic fields. In the present work, spray deposition is applied to prepare perpendicular anisotropic magnetic hybrid films by controlling the orientation of strontium hexaferrite nanoplatelets inside ultra-high-molecular-weight DBC polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) films. During spray deposition, the evolution of DBC morphology and the orientation of magnetic nanoplatelets are monitored with in situ grazing-incidence small-angle X-ray scattering (GISAXS). For reference, a pure DBC film without nanoplatelets is deposited with the same conditions. Solvent-controlled magnetic properties of the hybrid film are proven with solvent vapor annealing (SVA) applied to the final deposited magnetic films. Obvious changes in the DBC morphology and nanoplatelet localization are observed during SVA. The superconducting quantum interference device data show that ferromagnetic hybrid polymer films with high coercivity can be achieved via spray deposition. The hybrid films show a perpendicular magnetic anisotropy before SVA, which is strongly weakened after SVA. The spray-deposited hybrid films appear highly promising for potential applications in magnetic data storage and sensors.

Nematic Order of γ-Fe2O3 Nanoparticles in Dispersions in A Shear Flow and A Magnetic Field

Magnetic dispersions of nanoparticles have applications in magnetic data storage devices such as magnetic tapes and disks...

Robust Monolayer Exchange-Bias Effect in Molecular Crane-Pulley Response at Magnetic Surface

Exchange-bias effect is a widely investigated topic for spintronic applications in magnetic data storage read heads and spin-valve sensors. This effect is observed in bilayers of magnetic materials comprising of a soft ferromagnet (FM) and an antiferromagnet (AFM). In the last few years, unexpected observations of such an effect in ferromagnet-molecule heterostructures has raised curiosity in probing their underlying mechanism for potential technological applications. Here, we report our interface study between thin films of $\mathrm{Fe}$ and monolayer metal-phthalocyanine (MPc) molecules providing evidence of a robust exchange bias in zero-field cooled devices that is stable even after multiple training cycles. We ascribe the underlying mechanism to a combination of surface magnetic hardening and weakening of interlayer magnetic exchange that decouples the surface MPc-$\mathrm{Fe}$ hard magnetic layer from the soft switchable $\mathrm{Fe}$ layer underneath. We refer to this combined response to a molecular crane-pulley effect arising from the strong $\ensuremath{\pi}\ensuremath{-}d$ hybridization induced changes in the magnetization properties of surface $\mathrm{Fe}$ relative to the underlying film. Furthermore, analysis of our in-plane angle-dependent anisotropy magnetoresistance measurements reveal a surprisingly large biaxial anisotropy of the hard-surface layer with switching field exceeding 7 T. These studies provide us the opportunity to engineer the form of magnetic anisotropy at these spin interfaces.

Unraveling the properties of sharply defined submicron scale FeCu and FePd magnetic structures fabricated by electrodeposition onto electron-beam-lithographed substrates

In this work, Fe–X (X = Cu, Pd) submicron-scale structures were electrodeposited onto pre-patterned substrates prepared by e-beam lithography. The FeCu and FePd (with reduced Pd content) systems were investigated as attractive candidates for a variety of potential applications in magnetic data storage and biomedicine. Confined growth in the restricted cavities resulted in a nanoscale grain size leading to well-defined geometries with sharp edges and corners and an average height of up to 215 nm. Specifically, nine 100 μm × 100 μm arrays of three geometries (cylindrical, rectangular and cruciform) in three different sizes were created. In addition, the total deposition time ranged from 3.5 s (FeCu) to 200 s (FePd), i.e. much faster than by traditional physical vapor deposition approaches and was performed at ambient conditions. Magnetic force microscopy for the cylindrical and cruciform structures revealed virtually no contrast at zero field, suggesting magnetic curling effects (instead of coherent rotation) during magnetization reversal. These curling effects result in low values of remanent magnetization, which is advantageous in minimizing dipolar interactions between the structures either when they are deposited onto the substrate or eventually dispersed in a liquid (e.g. in biomedical applications, as drug delivery carriers, where particle agglomeration is undesirable).

Self-Assembly of Large Magnetic Nanoparticles in Ultrahigh Molecular Weight Linear Diblock Copolymer Films.

The development of diblock copolymer (DBC) nanocomposite films containing magnetic nanoparticles (NPs) with diameters (D) over 20 nm is a challenging task. To host large iron oxide NPs (Fe3O4, D = 27 ± 0.6 nm), an ultrahigh molecular weight (UHMW) linear DBC polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) is used as a template in the present work. Due to hydrogen bonding between the carboxylic acid ligands of the NPs and the ester groups in PMMA, the NPs show an affinity to the PMMA block. The localization of the NPs inside the DBC is investigated as a function of the NP concentration. At low NP concentrations, NPs are located preferentially at the interface between PS and PMMA domains to minimize the interfacial tension caused by the strong segregation strength of the UHMW DBC. At high NP concentrations (≥10 wt %), chain-like NP aggregates (a head-to-tail orientation) are observed in the PMMA domains, resulting in a change of the morphology from sphere to ellipsoid for part of the PMMA domains. Magnetic properties of the hybrid films are probed via superconducting quantum interference device magnetometry. All hybrid films show ferrimagnetism and are promising for potential applications in magnetic data storage.

Magnetization Studies on Tb–Fe and Tb–Fe–Co Thin Films

Magnetization studies were carried out on Tb-Fe and Tb-Fe-Co thin films, prepared using magnetron co-sputtering technique. The films Tb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">25</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">75</sub> and Tb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">69</sub> were found to have perpendicular magnetic anisotropy (PMA) both at 25 and 300 K. In Tb-Fe-Co films, all the films were observed to exhibit planar anisotropy at 25 K, due to the increase of strain-induced anisotropy as a result of large magnetostriction at low temperatures leading to the development of in-plane anisotropy. PMA was observed in the films Tb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">35</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">37</sub> Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">28</sub> , Tb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">56</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">25</sub> Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sub> , and Tb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">63</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</sub> at 300 K. The Curie temperatures (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> ) of both TbxFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">100-x</sub> and Tb-Fe-Co films were found to be above room temperature (RT). Observing the Curie temperatures well above the RT, with the existence of PMA at RTs, is an interesting object in these films to find in magnetic data storage applications.

Optically pumped Floquet states of magnetization in ferromagnets.

Floquet states have been the subject of great research interest since Zel'dovich's pioneering work on the quasienergy of a quantum system influenced by a temporally periodic action. Nowadays, periodic modulation of the system Hamiltonian is achieved mostly by microwaves, leading to novel exciting phenomena in condensed matter physics. On the other hand, nonthermal optical control of magnetization at picosecond time scales is currently a highly appealing research topic for potential applications in magnetic data storage. Here we combine these two concepts to theoretically investigate Floquet states in the system of exchange-coupled spins in a ferromagnet. Periodic perturbation of the magnetization of an iron-garnet film by circularly polarized femtosecond laser pulses is shown to establish the magnetization dynamics behaving like Floquet states. An external magnetic field allows tuning of the Floquet states, leading to pronounced increase in the precession amplitude by one order of magnitude at the center of the Brillouin zone, i.e., when the precession frequency is a multiple of the laser pulse repetition rate. Floquet states might potentially allow for parametric generation of magnetic oscillations. The observed phenomena expand the capabilities of coherent ultrafast optical control of magnetization and pave the way for their application in quantum computation or data processing.

Adsorption-induced pyramidal distortion of the trimetallic nitride core inside the endohedral fullerene Sc3N@C80 on the Ag(111) surface

Our ability to understand and tailor metal-organic interfaces is mandatory to functionalize organic complexes for next generation electronic and spintronic devices. For magnetic data storage applications, metal-carrying organic molecules, so called single molecular magnets (SMM) are of particular interest as they yield the possibility to store information on the molecular scale. In this work, we focus on the adsorption properties of the prototypical SMM Sc3N@C80 grown in a monolayer film on the Ag(111) substrate. We provide clear evidence of a pyramidal distortion of the otherwise planar Sc3N core inside the carbon cage upon the adsorption on the Ag(111) surface. This adsorption induced structural change of the Sc3N@C80 molecule can be correlated to a charge transfer from the substrate into the lowest unoccupied molecular orbital of Sc3N@C80, which significantly alters the charge density of the fullerene core. Our comprehensive characterization of the Sc3N@C80-Ag(111) interface hence reveals an indirect coupling mechanism between the Sc3N core of the fullerene molecule and the noble metal surface mediated via an interfacial charge transfer. Our work shows that such an indirect coupling between the encapsulated metal centers of SMM and metal surfaces can strongly affect the geometric structure of the metallic centers and thereby potentially also alters the magnetic properties of SMMs on surfaces.

Enhancing the perpendicular magnetic anisotropy of 1T-FeCl2 monolayer by applying strain: first-principles study

In consideration of importance of enhancing the magnetic anisotropy in ferromagnetic two-dimensional materials for their applications in magnetic data storage and spintronic devices, the structural stability and magnetic stability of FeCl2 monolayer in the 1T phase (1T-FeCl2 monolayer) under different strains and the influence of strain on magnetic stability and perpendicular magnetic anisotropy (PMA) of the 1T-FeCl2 monolayer are investigated using first-principles calculations. It is found that 1T-FeCl2 monolayer under different strains are stable at the room temperature by calculating the phonon dispersion and ab initio molecular dynamics (MD) simulations. Ferromagnetic is always the ground state of the unstrained and strained 1T-FeCl2 monolayer under different strains and the ferromagnetic stability can be enhanced by applying compressive strain. The magnetic anisotropy energy (MAE) of the unstrained 1T-FeCl2 monolayer is positive and the magnetization axis is perpendicular to the 1T-FeCl2 layer. As compressive strain increases, the positive contribution to MAE from SOC interaction between dx2-y2(dxy) and dyz(dxz) states increase, which lead to the MAE of the 1T-FeCl2 monolayer can be enhanced. On the contrary, the tensile strain can make the MAE of the 1T-FeCl2 monolayer weaken. Our results show that strain engineering is an effective approach to enhance PMA of 1T-FeCl2 monolayer.

Piezoelectric control of magnetoelectric coupling driven non-volatile memory switching and self cooling effects in FE/FSMA multiferroic heterostructures

The manipulation of magnetic states and materials' spin degree-of-freedom via a control of an electric (E-) field has been recently pursued to develop magnetoelectric (ME) coupling-driven electronic data storage devices with high read/write endurance, fast dynamic response, and low energy dissipation. One major hurdle for this approach is to develop reliable materials which should be compatible with prevailing silicon (Si)-based complementary metal–oxide–semiconductor (CMOS) technology, simultaneously allowing small voltage for the tuning of magnetization switching. In this regard, multiferroic heterostructures where ferromagnetic (FM) and ferroelectric (FE) layers are alternatively grown on conventional Si substrates are promising as the piezoelectric control of magnetization switching is anticipated to be possible by an E-field. In this work, we study the ferromagnetic shape memory alloys based PbZr0.52Ti0.48O3/Ni50Mn35In15 (PZT/Ni-Mn-In) multiferroic heterostructures, and investigate their potential for CMOS compatible non-volatile magnetic data storage applications. We demonstrate the voltage-impulse controlled nonvolatile, reversible, and bistable magnetization switching at room temperature in Si-integrated PZT/Ni-Mn-In thin film multiferroic heterostructures. We also thoroughly unveil the various intriguing features in these materials, such as E-field tuned ME coupling and magnetocaloric effect, shape memory induced ferroelectric modulation, improved fatigue endurance as well as Refrigeration Capacity (RC). This comprehensive study suggests that these novel materials have a great potential for the development of unconventional nanoscale memory and refrigeration devices with self-cooling effect and enhanced refrigeration efficiency, thus providing a new venue for their applications.

Ni-Co Alloy and Multisegmented Ni/Co Nanowire Arrays Modulated in Composition: Structural Characterization and Magnetic Properties

Design of novel multisegmented magnetic nanowires can pave the way for the next generation of data storage media and logical devices, magnonic crystals, or in magneto-plasmonics, among other energy conversion, recovery, and storage technological applications. In this work, we present a detailed study on the synthesis, morphology, structural, and magnetic properties of Ni, Co, and Ni-Co alloy and multisegmented Ni/Co nanowires modulated in composition, which were grown by template-assisted electrodeposition employing nanoporous anodic aluminum oxide as patterned templates. X-ray diffraction, and scanning and high-resolution transmission electron microscopies allowed for the structural, morphological, and compositional investigations of a few micrometers long and approximately 40 nm in diameter of pure Ni and Co single elements, together with multisegmented Ni/Co and alloyed Ni-Co nanowires. The vibrating sample magnetometry technique enabled us to extract the main characteristic magnetic parameters for these samples, thereby evaluating their different anisotropic magnetic behaviors and discuss them based on their morphological and structural features. These novel functional magnetic nanomaterials can serve as potential candidates for multibit magnetic systems in ultra-high-density magnetic data storage applications.

A novel magnetoelectric memory cell based on bilayer ferroelectric films of (1 − x)[Ba(Zr0.2Ti0.8)O3]–x(Ba0.7Ca0.3TiO3)

We demonstrate that a thin film magnetoelectric memory cell, comprised of Fe70Ga30 sputtered on top of bilayer ferroelectric films which consists of a tetragonal (T) 0.7Ba(Zr0.2Ti0.8)O3–0.3(Ba0.7Ca0.3TiO3) (70BZT–30BCT) film deposited on a rhombohedral (R) 0.3Ba(Zr0.2Ti0.8)O3–0.7(Ba0.7Ca0.3TiO3) (30BZT–70BCT) film. The insertion of rhombohedral layer improves the quality of the films and enhances the piezoelectric properties, which could be attributed to that the ferroelectric domains are tethered only by a soft R under layer, and not by the hard substrate. The working mechanism is that the 70BZT–30BCT layer acquires different strain states when an electric field is applied to it. Mechanical transduction couples this strain to the mechanically coupled Fe70Ga30 layer, which then changes its magnetic anisotropy and thus the magnetoresistance. The high (low) resistance states were realized when different voltages were applied due to the anisotropy magnetoresistance of Fe70Ga30 films. The demonstrated magnetoelectric memory device using resistance as the media and electric field as the writing field shows great promises towards exploring magnetoelectric devices for low-power and high density magnetic data storage applications.

Fabrication and characterization of a magnetoelectric memory cell of 50Ba(Zr0.2Ti0.8)O3–50Ba0.7Ca0.3TiO3/Fe70Ga30

We present a simple all-thin-film magnetoelectric memory cell with ferromagnetic film of Fe70Ga30 grown on ferroelectric film of 50Ba(Zr0.2Ti0.8)O3–50Ba0.7Ca0.3TiO3 (50BZT-50BCT) based on converse magnetoelectric effect. The heterostructure exhibits well-defined magnetic and piezoelectric behaviors. The 50BZT-50BCT layer acquires different strain states when an electric field is applied to the cell. Mechanical transduction couples this strain to the mechanically coupled Fe70Ga30 layer, which then changes its magnetic anisotropy and thus the magnetoresistance. Thus, a magnetoelectric memory cell with resistance as the media and electric field as the writing field was realized. The demonstrated electric field control of resistance states is a significant step towards exploring magnetoelectrically controlled spintronic devices for low-power and high density magnetic data storage applications.

Patterning of magnetic thin films and multilayers using nanostructured tantalum gettering templates.

This work demonstrates that a nonmagnetic thin film of cobalt oxide (CoO) sandwiched between Ta seed and capping layers can be effectively reduced to a magnetic cobalt thin film by annealing at 200 °C, whereas CoO does not exhibit ferromagnetic properties at room temperature and is stable at up to ∼400 °C. The CoO reduction is attributed to the thermodynamically driven gettering of oxygen by tantalum, similar to the exothermic reduction-oxidation reaction observed in thermite systems. Similarly, annealing at 200 °C of a nonmagnetic [CoO/Pd]N multilayer thin film sandwiched between Ta seed and Ta capping layers results in the conversion into a magnetic [Co/Pd]N multilayer, a material with perpendicular magnetic anisotropy that is of interest for magnetic data storage applications. A nanopatterning approach is introduced where [CoO/Pd]N multilayers is locally reduced into [Co/Pd]N multilayers to achieve perpendicular magnetic anisotropy nanostructured array. This technique can potentially be adapted to nanoscale patterning of other systems for which thermodynamically favorable combination of oxide and gettering layers can be identified.

Effect of electric-field on the perpendicular magnetic anisotropy and strain properties in CoFeB/MgO magnetic tunnel junctions

In this article, we investigate the effect of electric-field on the perpendicular magnetic anisotropy (PMA) and strain properties in nanoscaled CoFeB/MgO magnetic tunnel junction using tunnel magnetoresistance and piezoresponse force microscopy (PFM) measurements, respectively. We show that while the PMA change under electric-field is consistent with the previous reports, the PFM data show that the applied electric-field induces strain in a nanoscaled MgO. We demonstrate that the development of compressive and tensile strains corresponding to different polarities of applied electric-field. We discuss the interplay between the electric-field controlled PMA and strain properties. Our results may accelerate the development of magnetoelectrically controlled spintronic devices for low-power and high-density magnetic data storage applications.

Relevance of hybridization and filling of 3d orbitals for the Kondo effect in transition metal phthalocyanines.

Magnetic organic molecules, such as 3d transition metal phthalocyanines (TMPc), exhibit properties which make them promising candidates for future applications in magnetic data storage or spin-based data processing. Due to their small size, however, TMPc molecules are prone to quantum effects. For example, the interaction of uncompensated molecular spins with conduction electrons of the substrate may lead to the formation of a many-body singlet state, which gives rise to the so-called Kondo effect. Although the Kondo effect of TMPc molecules has been the object of several investigations, a consistent picture to describe under which conditions a Kondo state is formed is still missing. Here, we study the Kondo properties of MnPc on Ag(001) by means of the low-temperature scanning tunneling spectroscopy (LT-STS) measurements. Differential conductance dI/dU spectra reveal a zero-bias peak that is localized on the Mn ion site. Ab initio calculations combined with a many-body treatment of the multiorbital interaction show that the local Hund coupling favors the high-spin configuration on the 3d shell of the central TM atom. Therefore, each orbital gets close to its individual half-filling creating the necessary condition for many of the 3d orbitals to contribute to the observed Kondo resonance. This, however, happens only for the 3dz(2) orbital, whose hybridization to the substrate is much stronger than for the other orbitals thanks to its shape and its orientation.

Grain boundary diffusion induced reaction layer formation in Fe/Pt thin films

The solid-state reaction in Pt(15 nm)/Fe(15 nm) and Pt(15 nm)/Ag(10 nm)/Fe(15 nm) thin films after post-annealing at 593 K and 613 K for different annealing times has been studied. The structural properties of these samples were investigated by various methods including depth profiling with secondary neutral mass spectrometry, transmission electron microscopy, and X-ray diffraction. It is shown that after annealing at the above temperatures where the bulk diffusion processes are still frozen, homogeneous reaction layers of FePt and FePt with about 10 at.% Ag, respectively, have been formed. Corresponding depth profiles of the element concentrations revealed strong evidence that the formation mechanism is based on a grain boundary diffusion induced solid-state reaction in which the reaction interfaces sweep perpendicularly to the original grain boundary. Interestingly, X-ray diffraction indicated that in both thin-film systems after the solid-state reaction the ordered L10 FePt phase, which is the requested phase for future magnetic data storage applications, is also present.