Co2FeSi Films Research Articles

Surface Morphology and Exchange Bias Anisotropy Studies in Large Area Deposited Co2FeSi Ir50Mn50 Multi Layers For Spintronic Applications

Surface morphology and magnetic properties of ferromagnetic Heusler alloy Co2FeSi thin films and their multi-layers with anti-ferromagnetic Ir50Mn50, which find applications in spintronic devices were investigated. The sputtering process flow for large area deposition of thin films on 3 inch size thermally oxidized single crystal Si(100)/SiO2 substrates have been developed by optimizing the sputtering geometry and other process parameters. A uniform film composition, thickness, smooth surface, good crystallinity and magnetic properties have been achieved in the films over 3-inch size wafers. The isotropic magnetic properties such as saturation/remanent magnetizations, coercivity were achieved in Co2FeSi films deposited on 3-inch size Si(100)/SiO2 wafers with 15 nm Cr buffer layer. An exchange bias anisotropy has been established in Co2FeSi/IrMn multilayer by magnetic annealing process using in-house made magnetic annealing set up. A maximum exchange bias anisotropy field, Hex of 178 Oe and low coercivity, Hc of 85 Oe has been achieved in the Co2FeSi/IrMn multilayer stacks suitable for magnetic tunnel junctions for spintronic applications.

Influence of ferromagnetic layer thickness on the Gilbert damping and magnetocrystalline anisotropy in PLD grown epitaxial Co2FeSi Heusler alloy thin films

In the present work, full Heusler alloy (FHA) Co2FeSi (CFS) epitaxial thin films with thickness (tCFS) ranging from 5–25 nm were grown by Pulse laser deposition (PLD) on MgO (001) substrates at an optimized deposition temperature of 600°C. Dynamic magnetization response of PLD-grown CFS thin films was systematically investigated as a function of tCFS. Thickness-dependent structural and magnetic correlation exhibit a non-monotonic variation in Gilbert damping parameter, α. The ferromagnetic resonance (FMR) investigation revealed that the presence of lattice strain and a lower degree of atomic ordering in the thinner FHA CFS films, results in additional enhancement of α. The lowest α value of 4×10−3 is obtained from the theoretical fit of experimental data in a 20 nm thick film. This low value of α is suitable in magnonic devices, such as spin-transfer torque magnetic random-access memories (STT-MRAMs) where an efficient spin injecting source from a FHA ferromagnet to a non-magnetic interface is required. Further, in-plane angle-dependent (φ-variation) FMR measurements of the sample yield an intrinsic four-fold magnetocrystalline anisotropy (MCA) along with the presence of uniaxial anisotropy that has non-monotonicity with tCFS. A significant value of cubic anisotropy constant of 5.16×105erg/cm3 has been obtained in the film with a thickness of around 15nm. Further investigation suggests that uniaxial anisotropy in the CFS/MgO film is a combination of strain-induced magneto-elastic and interface-related contribution that is intrinsic in nature. The experimental observations have been verified by using micromagnetic simulations run on the epitaxial crystal structure. FMR mode position and linewidth of varied thickness CFS films are generated by micromagnetic simulations utilizing the Landau–Lifshitz–Gilbert formalism.

Giant magnetoelectric effect in an L21-ordered Co2FeSi/Pb(Mg1/3Nb2/3)O3-PbTiO3 multiferroic heterostructure

We experimentally show a giant magnetoelectric (ME) effect at room temperature in an interfacial multiferroic heterostructure consisting of L21-ordered Co2FeSi and Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT). Molecular beam epitaxy growth at 400 °C enables us to obtain epitaxial and L21-ordered Co2FeSi films on PMN-PT(001). For the epitaxial Co2FeSi/PMN-PT heterostructure, the remanent magnetization state can be largely modulated by varying electric fields. We note that the room-temperature ME coupling coefficient (α) is estimated to be 6.0–6.3 ×10−6 s/m, comparable to the highest α value reported previously. Nonvolatile and repeatable magnetization changes in remanent states are also demonstrated. These results will pave the way for room-temperature electric-field control of the magnetization of half-metallic Heusler alloys in high-performance spintronic devices.

Strain‐Controlled Spin Wave Excitation and Gilbert Damping in Flexible Co2FeSi Films Activated by Femtosecond Laser Pulse

AbstractThe dynamic response of magnetic order to optical excitation at sub‐picosecond scale has offered an intriguing alternative for magnetism manipulation. Such ultrafast optical manipulation of magnetism has become a fundamental challenging topic with high implications for future spintronics. Here, this study demonstrates such manipulation in Co2FeSi films grown on flexible polyimide substrate, and demonstrates how the magneto‐optical interaction can be modified by using strain engineering which in turn triggers the excitation of both dipolar and exchange spin waves modes. Furthermore, Gilbert damping and spin‐orbit coupling in Co2FeSi can both be tuned significantly by altering the magnitude and type of applied strain, suggesting an appealing way to manipulate spin wave propagation. These results develop the optical manipulation magnetism into the field of spin wave dynamics, and open a new direction in the application of spin orbitronics and magnonics devices using strain engineering.

Magneto-optical Kerr microscopy investigation of magnetization reversal in Co2FeSi Heusler alloy thin films

Magneto-optical Kerr effect microscopy investigation of magnetocrystalline anisotropy and the magnetization reversal (MR) process in Co2FeSi (CFS) Heusler alloy thin films reveals the following: Regardless of the strength of the anti-site atomic disorder, all CFS films of fixed thickness (t = 50 nm) exhibit variations in the remanent magnetization (Mr) and coercive field (Hc) with the “in-plane” magnetic field (H) angle, φH, that are characteristic of the “in-plane” uniaxial anisotropy (UA) with an easy axis along φH = 0°. The observed variations with the field-angle are well described by the two-phase pinning (TP) model. Exceptions to this rule are the films with t ≥ 25 nm, having a maximum B2 atomic order, which show completely different angular variations in Mr and Hc. In such exceptional cases, we find that the TP model reproduces Mr(φH) and Hc(φH) only when it takes into account two mutually exclusive UAs, UA1 and UA2, with easy axes perpendicular to one another and UA1 ≫ UA2. When H points along the easy axis (φH = 0°), MR in all CFS films proceeds through the nucleation of reverse domains and their subsequent growth by domain wall movement as H increases. Atomic disorder has essentially no effect on the MR process, but the domain wall pinning at defects/imperfections affects the magnitudes of Hc and the UA field, Hk. At φH ≃ 45°, MR takes place through the formation of ripple domains. As H increases, the reverse domains grow at the expense of ripple domains, and a single domain configuration is established at high fields. When φH = 90°, MR in all films involves nucleation and subsequent growth of reverse domains by the field-induced movement of the 180° domain walls.

Growth of ferromagnetic Co[formula omitted]FeSi films on flexible Ge(111)

For flexible semiconductor spintronic devices, we explore the growth of one of the ferromagnetic full-Heusler alloys, Co2FeSi, on a (111)-oriented pseudo-single-crystalline Ge/polyimide flexible template. Using a low-temperature molecular beam epitaxy (MBE) technique, crystalline Co2FeSi films are obtained on the flexible Ge at less than 80 °C. An MBE-grown Ge layer on the flexible Ge enables to improve magnetic properties of the Co2FeSi films. This work is an important step of high-performance flexible spintronics with ferromagnetic full-Heusler alloys.

Improvement of high-frequency properties of Co2FeSi Heusler films by ultrathin Ru underlayer**Project supported by the National Natural Science Foundation of China (Grant Nos. 11674187 and 51871127) and the Fund from the Technology on Electronic Test & Measurement Laboratory (Grant No. 6142001180103).

Heusler Co2FeSi films with a uniaxial magnetic anisotropy and high ferromagnetic resonance frequency fr were deposited by an oblique sputtering technique on Ru underlayers with various thicknesses tRu from 0 nm to 5 nm. It is revealed that the Ru underlayers reduce the grain size of Co2FeSi, dramatically enhance the magnetic anisotropy field HK induced by the internal stress from 242 Oe (1 Oe = 79.5775 A⋅m−1) to 582 Oe with an increment ratio of 2.4, while a low damping coefficient remains. The result of damping implies that the continuous interface between Ru and Co2FeSi induces a large in-plane anisotropic field without introducing additional external damping. As a result, excellent high-frequency soft magnetic properties with fr up to 6.69 GHz are achieved.

Great Differences between Low-Temperature Grown Co2FeSi and Co2MnSi Films on Single-Crystalline Oxides

Using extremely low synthesis temperatures in molecular beam epitaxy (MBE) conditions on MgO(001), SrTiO3(001), and MgAl2O4(001), we find great differences in the crystallinity and magnetic properties between Co-based full-Heusler-alloy Co2FeSi and Co2MnSi films. For example, while L21-ordered Co2FeSi films can be demonstrated on all the oxides even at less than 80 °C, only the B2-ordered and amorphous Co2MnSi films can be obtained. Considering the experimental results and the findings obtained from theoretical calculations, we can conclude that the stability of the Heusler/oxide interfaces and the alloying energy of the disordered Heusler alloys are two of the most important factors for the low-temperature growth of epitaxial Co2FeSi and Co2MnSi films on these oxides. We suggest that Co2FeSi is more suitable for low-temperature formed spintronic devices than Co2MnSi.

Thickness dependent structural ordering and magnetic properties of Co2FeSi films with or without a Cr buffer layer

We have performed a detailed study on the structure and magnetic properties for Co2FeSi (CFS) alloy films deposited on the MgO(0 0 1) substrates with or without a Cr buffer layer. With the increase of CFS thickness, the structure ordering degree increases, leading to an improved biaxial magnetic anisotropy. Nevertheless, in spite of the reduced lattice misfit between MgO and CFS, XRD results reveal that the insertion of a 2.5 nm thick Cr layer could give rise to the loss of CFS ordering, which has been ascribed to the interfacial diffusion of Cr atoms caused by thermal annealing. As the Cr buffer thickness is increased more than 10 nm, it is found that the chemically ordered CFS structure reappears, showing a weak four-fold symmetry. Nevertheless, as compared to the CFS films without a Cr buffer, the biaxial magnetic anisotropy rotates by 45°, with two magnetic easy axes transforming from the directions of MgO〈1 1 0〉/CFS〈1 0 0〉 to MgO〈1 0 0〉/CFS〈1 1 0〉. We consider that the observed orientation transition of biaxial magnetic anisotropy results from the competition between the Cr/CFS interfacial contribution and the intrinsic bulk CFS contribution. Our results provide a better understanding of the evolution of crystalline structure and in-plane magnetic anisotropy with increasing the CFS and Cr layer thicknesses, which will be helpful for designing advanced spintronic devices.

Uniaxial anisotropy, intrinsic and extrinsic damping in Co2FeSi Heusler alloy thin films

Ferromagnetic resonance (FMR) technique has been used to study the magnetization relaxation processes and magnetic anisotropy in two different series of the Co2FeSi (CFS) Heusler alloy thin films, deposited on the Si (1 1 1) substrate by ultra high vacuum magnetron sputtering. While the CFS films of fixed (50 nm) thickness, deposited at different substrate temperatures (TS) ranging from room temperature (RT) to 600°C, constitute the series-I, the CFS films with thickness t varying from 12 nm to 100 nm and deposited at 550°C make up the series-II. In series-I, the CFS films deposited at TS = RT and 200°C are completely amorphous, the one at C is partially crystalline, and those at C, 550°C and 600°C are completely crystalline with B2 order. By contrast, all the CFS films in series-II are in the fully-developed B2 crystalline state. Irrespective of the strength of disorder and film thickness, angular variation of the resonance field in the film plane unambiguously establishes the presence of global ‘in-plane’ uniaxial anisotropy. The uniaxial anisotropy field decreases as the crystalline order in the films increases and goes through a minimum at t = 50 nm as a function of film thickness. Landau–Lifshitz–Gilbert damping and two-magnon scattering dominantly contribute to the line-broadening in both ‘in-plane’ and ‘out-of-plane’ configurations. The two-magnon scattering has larger magnitude in the amorphous films than in the crystalline ones. Angular variation of the linewidth in the film plane reveals that, in the CFS thin films of varying thickness, a crossover from the ‘in-plane’ local four-fold symmetry (cubic anisotropy) to local two-fold symmetry (uniaxial anisotropy) occurs as t exceeds 50 nm. Gilbert damping constant decreases monotonously from 0.047 to 0.0078 with decreasing disorder strength (increasing TS) and jumps from 0.008 for the CFS film with t = 50 nm to 0.024 for the film with t = 75 nm. Such variations of with TS and t are understood in terms of the changes in the total (spin-up and spin-down) density of states at the Fermi level caused by the disorder and film thickness. Spin pumping across the Co2FeSi film/Ta cap-layer interface makes negligible contribution to . We propose that disorder and/or the film thickness can be used as control parameters to tune , whose value is decisive in choosing a ferromagnetic film for a given spintronics application.

Diffuson contribution to anomalous Hall effect in disordered Co2FeSi thin films

A wide variation in the disorder strength, as inferred from an order of magnitude variation in the longitudinal resistivity of Co2FeSi (CFS) Huesler alloy thin films of fixed (50 nm) thickness, has been achieved by growing these films on Si(111) substrates at substrate temperatures ranging from room temperature (RT) to 600 C. An in-depth study of the influence of disorder on anomalous Hall resistivity,longitudinal resistivity(LR) and magnetoresistance, enabled by this approach, reveals the following. The side-jump mechanism gives a dominant contribution to anomalous Hall resistivity (AHR) in the CFS thin films, regardless of the degree of disorder present. A new and novel contribution to both LR and AHR characterized by the logarithmic temperature dependence at temperatures below the minimum, exclusive to the amorphous CFS films, originates from the scattering of conduction electrons from the diffusive hydrodynamic modes associated with the longitudinal component of magnetization, called diffusons. In these amorphous CFS films, the electron-diffuson, e d, scattering and weak localization (WL) mechanisms compete with that arising from the inelastic electron magnon, e m, scattering to produce the minimum in longitudinal resistivity, whereas the minimum in AHR is caused by the competing contributions from the e d and e m scattering, as WL does not make any contribution to AHR. In sharp contrast, in crystalline films, enhanced electron electron Coulomb interaction (EEI), which is basically responsible for the resistivity minimum, makes no contribution to AHR with the result that AHR does not exhibit a minimum.

Methods to induce perpendicular magnetic anisotropy in full-Heusler Co2FeSi thin layers in a magnetic tunnel junction structure

In this study, to obtain perpendicular magnetic tunnel junctions (p-MTJs) using half-metallic ferromagnets (HMFs), several methods were developed to induce perpendicular magnetic anisotropy (PMA) in full-Heusler Co2FeSi (CFS) alloy thin layers in an MTJ multilayer composed of a layered CFS/MgO/CFS structure. Oxygen exposure at 2.0 Pa for 10 min after deposition of the bottom CFS layer was effective for obtaining PMA in the CFS layer. One of the reasons for the PMA is the formation of nearly ideal CFS/MgO interfaces due to oxygen exposure before the deposition of the MgO layer. The annealing process was effective for obtaining PMA in the top CFS layer capped with a Pd layer. PMA was clearly observed in the top CFS layer of a Cr(40 nm)/Pd(50 nm)/bottom CFS(0.6 nm)/MgO(2.0 nm)/top CFS(0.6 nm)/ Pd(10 nm) multilayer, where the top CFS and Pd thin films were deposited at RT and subsequently annealed at 300°C. In addition to the continuous layer growth of the films, the crystalline orientation alignment at the top CFS/Pd interface probably attributes to the origin of PMA at the top CFS layer.

Influence of sputtering power on structural and magnetic properties of as-deposited, annealed and ERTA Co2FeSi films: A comparative study

We report the effect of sputtering power (200 W - 350 W) on the structural, topographical and magnetic properties of Co2FeSi (CFS) films deposited at ambient temperatures as compared to the films which were either annealed at 300 °C or were subjected to Electron beam Rapid Thermal Annealed (ERTA) treatment. The structural and morphological analyses reveal changes in their crystalline phases and particle sizes. All the as-deposited and annealed CFS films showed A2 phase crystal structure. Whereas the CFS film sputtered at 350 W followed by ERTA displayed the fully ordered L21 structure. The particles are spherical in shape and their sizes increased gradually with increase in the sputtering power of the as-deposited and annealed CFS films. However, ERTA CFS films had spherical as well as columnar (elongated) shaped grains and their grain sizes increased nonlinearly with sputtering power. M-H studies on as-deposited, annealed and ERTA CFS films show ferromagnetic responses. The comparatively stronger ferromagnetic response was observed for the ERTA samples with low saturation field which depends on the enrichment of fine crystallites in these films. This indicates that, apart from higher sputtering powers used for deposition of CFS films, ERTA process plays a significant role in the enhancement of their magnetic responses. 350 W ERTA film has the considerable saturation magnetization (∼816 emu/cc), coercivity (∼527 Oe) and a good squareness values at 100 K than at 300 K, which could originate from the spin wave excitation effect. Further, the optimized parameters to achieve a CFS film with good structural and magnetic properties are discussed from the perspective of spintronics.

Effect of disorder on the anomalous Hall conductivity of Co2FeSi thin films

The longitudinal resistivity and anomalous Hall resistivity of 50nm Co2FeSi films deposited on Si (100) substrate at different temperatures have been investigated as functions of disorder. The film deposited at 450°Chas minimum disorder and the lowest temperature (Tmin∼11K) at which resistivity goes through a minimum as a function of temperature. The film with the highest disorder has the largest Tmin, residual resistivity and absolute value of resistivity at any given temperature. The resistivity data have been analyzed taking into account the contributions from electron-electron scattering, electron-phonon scattering and disorder-induced enhanced electron-electron interaction, which dominates at low temperatures. The effect of Tmin is observed in Hall resistivity for all the samples. Anomalous Hall conductivity (AHC) is extremely sensitive to the degree of disorder present in the films and has the value 180S/cm at 300K for the most ordered TS450 film, which tallies well with the theoretically calculated value for the Co2FeSi alloy with L21 structure. The influence of disorder on the longitudinal resistivity and anomalous Hall effect has been discussed in detail.

Dynamic magnetic characteristics of obliquely sputtered Co2FeSi film with ultrahigh in-plane uniaxial anisotropy

We performed systematically studies on the magnetostatic and magnetodynamic properties of obliquely deposited Co2FeSi thin films. By varying the oblique deposition angle of Co2FeSi films, we induced a large in-plane uniaxial magnetic anisotropy field with the maximum value of 626.7 Oe at oblique angle of 39°, which significantly enhanced its zero-field ferromagnetic resonance (FMR) frequency up to 10.8 GHz. The magnetodynamic parameters such as Gilbert damping factor and exchange stiffness of Co2FeSi films were determined from the uniform FMR mode and the first perpendicular standing spin-wave, respectively. It is found that the Gilbert damping factor can be easily tuned from 0.006 to 0.013 by changing oblique deposition angle, whereas the exchange stiffness stays almost constant. These Co2FeSi films with tunable magnetic properties might be a good candidate for applications in both conventional and spintronics microwave devices.

Perpendicular Magnetic Anisotropy of Co2FexMn1−xSi Heusler Alloy Ultra-Thin Films

Film thickness, composition, and buffer layer dependences of perpendicular magnetic anisotropy (PMA) were investigated for ultrathin Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Mn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> Si Heusler alloy films. The perpendicular magnetization was achieved when the thickness of the Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> MnSi on the Pd buffer layer was 0.6 and 0.8 nm. For Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> FeSi, only a 0.6 nm thick film exhibited perpendicular magnetization. Effective uniaxial magnetic anisotropy energy (Keffu ) was 1-2 × 106 erg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . From the buffer layer dependence, it was revealed that perpendicular magnetization of Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> FeSi films was not achieved for a MgO or Cr buffer layer. These results imply that contributions from the Pd/Heusler alloy interface plays an important role in the PMA of ultrathin Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Mn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> Si Heusler alloy films.

Microwave ferromagnetic properties of as-deposited Co2FeSi Heusler alloy films prepared by oblique sputtering

The Co2FeSi films are deposited on Si (100) substrates by an oblique sputtering method at ambient temperature. It is revealed that the microwave ferromagnetic properties of Co2FeSi films are sensitive to sample position and sputtering power. It is exciting that the as-deposited films without any magnetic annealing exhibit high in-plane uniaxial anisotropy fields in a range of 200 Oe–330 Oe (1 Oe = 79.5775 Am−1), and low coercivities in a range of 5 Oe–28 Oe. As a result, high self-biased ferromagnetic resonance frequency up to 4.75 GHz is achieved in as-deposited oblique sputtered films. These results indicate that Co2FeSi Heusler alloy films are promising in practical applications of RF/microwave devices.

Electronic properties of Co2FeSi investigated by X-ray magnetic linear dichroism

We present experimental XMLD spectra measured on epitaxial (001)-oriented thin Co2FeSi films, which are rich in features and depend sensitively on the degree of atomic order and interdiffusion from capping layers. Al- and Cr-capped films with different degrees of atomic order were prepared by DC magnetron sputtering by varying the deposition temperatures. The local structural properties of the film samples were additionally investigated by nuclear magnetic resonance (NMR) measurements. The XMLD spectra of the different samples show clear and uniform trends at the L3,2 edges. The Al-capped samples show similar behavior as previous measured XMLD spectra of Co2FeSi0.6Al0.4. Thus, we assume that during deposition Al atoms are being implanted into the subsurface of Co2FeSi. Such an interdiffusion is not observed for the corresponding Cr-capped films, which makes Cr the material of choice for capping Co2FeSi films. We report stronger XMLD intensities at the L3,2 Co and Fe egdes for films with a higher saturation magnetization. Additionally, we compare the spectra with ab initio predictions and obtain a reasonably good agreement. Furthermore, we were able to detect an XMCD signal at the Si L-edge, indicating the presence of a magnetic moment at the Si atoms.

High-Frequency Ferromagnetic Properties of Nanocrystalline (Co&lt;sub&gt;2&lt;/sub&gt;FeSi)&lt;sub&gt;1-x&lt;/sub&gt;(Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;x &lt;/sub&gt;Heusler Alloy Films with Uniaxial Magnetic Anisotropy

A series of (Co2FeSi)1-x(Al2O3)xHeusler alloy films with various Al2O3-doping were prepared by an oblique sputtering method. It is exciting that the as-deposited films exhibit a very high in-plane uniaxial magnetic anisotropy (UMA) field up to 360 Oe and low coercivity of 12 Oe. Consequently, a very high self-bias ferromagnetic resonance frequency in excess of 5.02 GHz was obtained in as-deposited Co2FeSi films without any annealing. The good microwave ferromagnetic performances and the integrated circuits compatible fabrication process of Co2FeSi films make possible application in RF/microwave devices.

Effect of sputtering pressure and power on composition, surface roughness, microstructure and magnetic properties of as-deposited Co2FeSi thin films

The effect of sputtering pressure and power on the composition, surface roughness, structure, microstructure and magnetic properties of full Heusler type Co2FeSi films deposited on silicon (001) substrates at room temperature using DC magnetron sputtering technique was studied. The composition of the film was found to be influenced by both sputtering pressure and power. The films deposited at lower pressures (0.667–2Pa) and lower power (50–75W), which result in lower deposition rates, have compositions comparable with that of the target. The surface roughness of the films was found to be significantly affected by a change in sputtering pressure but not by a variation in sputtering power. Irrespective of the sputtering pressure and power, all the as-deposited Co2FeSi/Si(001) films exhibited A2 type disordered nanocrystalline structure. The grain size, however, was found to increase marginally with an increase in sputtering pressure and power. Analysis of magnetization curves of the films revealed that the films were soft ferromagnetic for all sputtering pressures and power. However, the coercivities, magnetization values and reversibility of zero field cooling and field cooling magnetization curves were found to depend critically on sputtering parameters.