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Study of the domain wall (DW) dynamics in ultrathin films with perpendicular magnetic anisotropy (PMA) opens the way to envisage the low-power and high-performance memory and logic devices. Here, we have studied the magnetization reversal and DW dynamics of Pt/Co/Pt ultrathin films having PMA. The Pt/Co/Pt ultrathin trilayers have been fabricated using molecular beam epitaxy (MBE) at room temperature. The DW velocity measurements were performed by bubble domain expansion method with an additional homemade coil in order to apply out-of-plane (OOP) field in the polar magneto-optic Kerr effect (P-MOKE)-based microscope. The DW motion is limited only in creep regime, and the maximum observed DW velocity is 32 mm/s. Further, it has been shown that the DW velocity can be enhanced via increasing Co thickness. [ABSTRACT FROM AUTHOR]

Domain wall (DW) statics and dynamics have been immensely studied for the last few decades in a disordered medium due to rich fundamental physics and spintronics applications. Here, we have studied the DW dynamics in Pt/CoFeB/MgO thin film with perpendicular magnetic anisotropy. We have observed an unusual behaviour in the DW dynamics which cannot be only explained via universal creep or depinning law. At low driving force, the sample follows the universal creep law; however, near the depinning field ( H d ), an excess velocity has been observed in DW dynamics in comparison to the usual creep law. We propose that, due to additional relaxation events near H d , the DW propagation length is increased and hence the DW velocity. The excess velocity has been modelled to a modified creep law. [ABSTRACT FROM AUTHOR]

Magnetron sputtering is a very versatile technique extensively employed for the deposition/growth of thin films. However, the deposition of desirable magnetic films is one of the challenges confronting magnetron sputtering owing to the shunting of magnetic flux by magnetic targets in conventional magnetron sputtering equipment. This flux shunting culminates in lower plasma density, non-uniform plasma confinement, and uneven erosion of magnetic targets, adversely affecting the growing films' thickness uniformity and chemical homogeneity—the latter can be particularly serious in magnetron co-sputtering. In this article, it is discussed that these issues can be avoided by cylindrical sputtering. As for planar sputtering, formerly offered technical solutions including the utilization of thin foils as magnetic targets, the deployment of gapped targets somewhat allowing the magnetic flux of the magnetron assembly, the employment of a target heating system increasing a magnetic target's temperature greater than or equal to its Curie temperature, facing target sputtering, magnetron sputtering assisted by coupled plasma inductively generated in an internal coil, and the generation of plasma remotely from magnetic targets (i.e., high target utilization sputtering) are scrutinized with their advantages/disadvantages being further examined. Finally, it is discussed that not only can auxiliary grid deployment mitigate/remove the issues of planar magnetron sputtering by modifying spatial plasma density distribution near the target but also it can solely shoulder the responsibility of ionization enhancement and plasma confinement for deposition of magnetic films. [ABSTRACT FROM AUTHOR]

This study considers the equiatomic CoCrNi alloy, a typical multi-principal element alloy (MPEA), which in bulk form, has shown superior mechanical properties and excellent oxidation and corrosion resistance. Such a combination of desirable characteristics motivates further research into the potential use of CoCrNi in thin-film form for various applications. This work aims to grow and optimize the deposition parameters of CoCrNi thin films and investigate their influence on the physical properties. The CoCrNi medium entropy alloy thin films were deposited onto Si/SiO2 substrates by direct current magnetron sputtering at different substrate temperatures and working gas pressures using a pre-alloyed target. The equiatomic polycrystalline composition was obtained at optimized pressure (2 mTorr) and temperature (400 °C). The electrical and magnetic properties were measured and contrasted with the physical properties of the bulk CoCrNi. The obtained magnetic properties indicate stabilization of the ferromagnetic phase in CoCrNi thin films. Anomalous Hall effect has been observed for all studied films. This work shows that deposition conditions (e.g., substrate temperature and working pressure) can be utilized to control the composition and microstructure and tailor the physical properties of the considered MPEA thin films for desired applications. [ABSTRACT FROM AUTHOR]

This paper reports the magnetic domain imaging and magnetization studies carried out on Fe thin films grown with different thicknesses, namely, 5, 15 nm, 30 nm, 50 nm, 75 nm and 100 nm. Films were grown on Si <100> at two different substrate temperatures, namely, room temperature and 550°C. Based on the detailed studies carried out, it was observed that Fe layer thickness and substrate temperature are important control parameters in tuning the magnetic anisotropy along the in-plane (IP) or out-of-plane (OOP) directions. A crossover from surface to volume anisotropy has been demonstrated with change in film thicknesses. Domain imaging studies carried out on Fe films grown at different substrate temperatures and with different thicknesses aided us to understand the magnetic anisotropy and magnetization reversal mechanisms. [ABSTRACT FROM AUTHOR]

The enhancement of coercive field values depending on the measurement angle in a perpendicularly magnetized continuous thin film and the asymmetries in its hysteresis loops are analyzed and discussed by means of Hall effect measurements. Anomalous Hall effect and planar Hall effect contributions to the Hall results are separated to make the asymmetric loops symmetrical. The magnetic properties of the sample are also measured by using a vibrating sample magnetometer and magneto-optic Kerr effect methods. The data obtained by the measurement systems are compared, and the differences in their results are discussed. The results of the work highlight the importance of choosing the correct setup for the measurements and the importance of the measurement angle for the Hall effect studies in magnetic thin films. [ABSTRACT FROM AUTHOR]

The magnetic and magnetoresistance properties of multilayered structures consisting of two different combinations of magnetic and nonmagnetic IrMn, Co, Cu, Ni, Py thin layers were studied in the temperature range of 10–300 K. Thin films were prepared by using conventional magnetic sputtering techniques in ultra-high vacuum conditions. The structural characterization was examined by X-ray reflectivity. Magnetic and electrical properties were studied by conventional dc magnetization and 4-probe resistivity measurements. A close relationship between magneto resistivity and the relative behavior of magnetic hysteresis of adjacent magnetic layers was observed. Very abrupt stepwise changes at coercive field regions of the soft magnetic layers were attributed to the so-called giant magnetoresistance effect at low temperatures in both combinations of the layers. [ABSTRACT FROM AUTHOR]

The structural, optical, magnetic, and electrical properties of Co2CrAl Heusler alloy magnetic thin films grown on n-type silicon (100) substrate (n-Si) and glass substrate were studied. The films were deposited using DC magnetron sputtering. X-ray diffraction (XRD) analysis confirmed the polycrystalline nature of the films. The effect of grain size on transmittance was investigated. Magnetic measurements revealed the presence of magnetic ordering in the films. Partial densities of states (PDOS) of the Co2CrAl were calculated by density functional theory (DFT) methods using the Vienna Ab initio Simulation Package (VASP). Co2CrAl thin film deposited over a silicon substrate was investigated for I–V characteristics. The electrical behaviour confirmed the existence of a Co2CrAl/n-Si Schottky contact, which suggests a spin injection phenomenon from Co2CrAl to n-Si by tunnelling through the lowered Schottky barrier. [ABSTRACT FROM AUTHOR]

Magnetic thin films of Fe/Cu/Fe and Fe/Cu/Ni multilayers on glass substrates were deposited by thermal evaporation route. The structure and morphology of multilayers were studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). Amorphous formation of the Fe and Ni in multilayer structures and the maximum surface roughness of about 6.11 nm for the Fe/Cu/Fe and 4.8 nm for the Fe/Cu/Ni thin films were observed. Also, magnetization behaviors in perpendicular and parallel fields to the surface were investigated. The behavior of the magnetization indicates a low 5-mT coercive field, the easy in-plane magnetization, and the formation of soft ferromagnetic structure. The giant magneto-impedance response (GMI) to the applied longitudinal magnetic field at 5-MHz frequency was obtained 70% for three-layer Fe/Cu/Fe. Also, the measurements for the Fe/Cu/Ni film show a peak in the external field of about Hext = 14 Oe and the GMI response of about 95% at 5-MHz frequency. This work provides a preliminary investigation into the high performance of multilayer-based GMI devices for sensor applications. [ABSTRACT FROM AUTHOR]

The effect of thickness on structural and magnetic properties of Co-rich Bi10Co16O38 (BCO) sillenite thin films is investigated systematically. BCO thin films are deposited using a simultaneous evaporation of Bi2O3, Co targets with RF-DC magnetron sputtering along with post-annealing procedure. The magnetic studies reveal an ordered magnetic nature below film thicknesses of 100 nm. Further, the temperature-dependent and field-dependent magnetic data is evaluated to comprehend the microstructure impact on to the magnetic nature of Co-rich sillenite thin films. [ABSTRACT FROM AUTHOR]

We discuss properties of proximity systems made of superconducting, ferromagnetic, and graphite nanoscale thin films. In superconducting-graphite proximity systems, we show how size quantization results in oscillations of the density of states with increasing graphite film thickness. In superconducting-ferromagnetic multilayers, we discuss the critical temperature variations of the proximity system as a function of ferromagnetic layer thickness and magnetic inhomogeneity. We also review the Josephson effect through a superconductor-ferromagnet-superconductor multilayer. In this context, we discuss the presence of a long-range odd-frequency triplet order parameter. [ABSTRACT FROM AUTHOR]

Array of dots have been designed by assembling a monolayer of polystyrene nanospheres (PN) on sputtered thin films having NiFe and Co composition with different thickness, ranging in the interval 20 ÷ 80 nm. Subsequently the films are nanopatterned using the nanospheres as a mask during sputter etching with Ar ions. A Reactive Ion Etching (RIE) process before sputter etching is used to control the final diameter of the magnetic dots that thus can be tailored as desired (typically ranging in the interval 250 ÷ 400 nm depending on the PN starting diameter). In addition, electron beam lithography has been exploited to obtain arrays of dots in NiFe thin films having approximately the same mean size and dot distance as in self-assembled samples. All films have been routinely characterized by SEM and AFM microscopy to evaluate the microstructure. Magnetic domain patterns at magnetic remanence and in the demagnetised state have been imaged by MFM microscopy technique. Room-temperature hysteresis properties have been measured by an alternating gradient force magnetometer. In general, the magnetization process in all patterned films has been observed to have features typical of a vortex whose nucleation field depends on sample thickness and mean dot dimension. A comparison between magnetic arrays of NiFe dots prepared by self-assembling of polystyrene nanospheres and electron beam lithography is presented to rule out the role of microstructure (i.e., order, size, and mutual distance of the magnetic dots) on magnetic properties. [ABSTRACT FROM AUTHOR]

The microstructure and magnetic properties of cobalt ferrite thin films deposited by the sputtering method on an FeO under-layer were investigated at different post-annealing temperatures. Results show that the FeO under-layer can accelerate the grain growth of cobalt ferrite films due to the phase transformation of the FeO under-layer at about 400°C-500°C. By introducing the FeO under-layer, cobalt ferrite nanocrystalline thin films with high coercivity can be obtained at lower post-annealing temperatures. [ABSTRACT FROM AUTHOR]

g/[BN/CoPt]/Ag and [BN/Ag/CoPt]/Ag thin films were deposited on glass substrates by magnetron sputtering and then annealed in vacuum at 600°C for 30 min. The structures and magnetic properties of CoPt/BN multilayer films were investigated as a function of Ag layer thickness. It was found that the face-centered tetragonal (fct) (001) texture of CoPt was improved greatly by introducing the Ag toplayer or sublayer together with an Ag underlayer. Good (001)-oriented growth, low intergrain interactions as well as high perpendicular anisotropy can be obtained in the Ag(3 nm)/[BN(2.5 nm)/CoPt(3 nm)]/Ag(7 nm) and [BN(2.5 nm)/Ag(2 nm)/CoPt(3 nm)]5/Ag(10 nm) films, which become potential candidates for ultrahigh density magnetic recording media. [ABSTRACT FROM AUTHOR]

In this paper we report structural, magnetic and transport properties of strongly textured NiMnSn thin films. The off-stoichiometric Heusler alloy films with 200 nm thickness were sputter-deposited on a MgO(100) substrate at 500 K and after annealed at 1000 K in UHV conditions. The textured growth was confirmed by x-ray diffraction in Bragg-Brentano geometry. The temperature dependence of the magnetic properties was measured by VSM and FMR methods. The electron transport measurements were carried out in function of temperature in 0 Oe and 50 kOe fields. All measurements corroborate the existence of the martensitic transformation in the film. Furthermore, transport measurements reveal an influence of the magnetic field on the transition temperature. [ABSTRACT FROM AUTHOR]

The morphological, structural, and magnetic properties of Co and Ni films of different thicknesses grown by RF sputtering on a Si-SiO substrate and submitted to controlled diffusion of atoms on the substrate (de-wetting) are studied through X-ray diffraction (XRD), atomic force microscopy, X-ray photoelectron spectroscopy, and alternating-gradient magnetometry. For both metals, de-wetting treatment leads to the growth of non-percolating, metallic nanoislands characterized by a distribution of sizes and aspect ratios. XRD spectra reveal a polycrystalline multi-component structure evolving by effect of de-wetting and directly affecting the magnetic properties of films. The magnetic response after de-wetting is consistent with the formation of a nanogranular magnetic phase characterized by a complex, thickness-dependent magnetic behavior originating from the simultaneous presence of superparamagnetic and blocked-particle contributions. At intermediate film thickness (around 10 nm), a notable enhancement in magnetic coercivity is observed for both metals with respect to the values measured in precursor films and in their bulk counterparts. [ABSTRACT FROM AUTHOR]

The magnetic properties of Ni thin films, in the range 20–500 nm, at the crystalline-nanocrystalline interface are reported. The effect of thickness, substrate and substrate temperature has been studied. For the films deposited at ambient temperatures on borosilicate glass substrates, the crystallite size, coercive field and magnetization energy density first increase and achieve a maximum at a critical value of thickness and decrease thereafter. At a thickness of 50 nm, the films deposited at ambient temperature onto borosilicate glass, MgO and silicon do not exhibit long-range order but are magnetic as is evident from the non-zero coercive field and magnetization energy. Phase contrast microscopy revealed that the grain sizes increase from a value of 30–50 nm at ambient temperature to 120–150 nm at 503 K and remain approximately constant in this range up to 593 K. The existence of grain boundary walls of width 30–50 nm is demonstrated using phase contrast images. The grain boundary area also stagnates at higher substrate temperature. There is pronounced shape anisotropy as evidenced by the increased aspect ratio of the grains as a function of substrate temperature. Nickel thin films of 50 nm show the absence of long-range crystalline order at ambient temperature growth conditions and a preferred [111] orientation at higher substrate temperatures. Thin films are found to be thermally relaxed at elevated deposition temperature and having large compressive strain at ambient temperature. This transition from nanocrystalline to crystalline order causes a peak in the coercive field in the region of transition as a function of thickness and substrate temperature. The saturation magnetization on the other hand increases with increase in substrate temperature. [ABSTRACT FROM AUTHOR]

Dry etching of the magnetic thin films such as Ta, Fe, Co, NiFe, NiFeCo, and MnNi was carried out in inductively coupled plasmas of Cl2/Ar mixture. All the magnetic materials went through a maximum etch rate at 25% Cl2. The effects of the ICP source power and the rf chuck power on the etch rate and the surface roughness were quite dependent of the materials. An ion-enhanced chemical etch mechanism was important for the magnetic films. The surface roughness of the etched samples was relatively constant of the rf chuck power up to 200 W, but a rougher surface at a higher rf power was obtained. Post-etch cleaning of the etched samples in de-ionized water reduced the chlorine residues substantially. [ABSTRACT FROM AUTHOR]

The ferromagnetic order is modified near the surface of a magnetic crystal. This modification is studied most clearly in magnetic thin films consisting of only a few atomic layers. Some essential features of the theoretical description are reported as a basis for the discussion of experiments. The main experimental problem is the preparation of flat single crystal films; the real structure of the best available films is discussed. Their magnetic properties are compared with theoretical predictions. Furthermore, methods and results are reported for probing the magnetic properties of surfaces, by their interaction with low energy electrons. [ABSTRACT FROM AUTHOR]

Dry etching of multilayer magnetic thin film materials is necessary for the development of sensitive magnetic field sensors and memory devices. The use of high ion density electron cyclotron resonance (ECR) plasma etching for NiFe, NiFeCo, TaN, and CrSi in SF6/Ar, CH4/H2/Ar, and Cl2/Ar plasmas was investigated as a function of microwave source power, rf chuck power, and process pressure. All of the plasma chemistries are found to provide some enhancement in etch rates relative to pure Ar ion milling, while Cl2/Ar provided the fastest etch rate for all four materials. Typical etch rates of 3000Å/min were found at high microwave source power. Etch rates of these metals were found to increase with rf chuck power and microwave source power, but to decrease with increasing pressure in SF6/Ar, CH4/H2/Ar, and Cl2/Ar. A significant issue with Cl2/Ar is that it produces significant metal-chlorine surface residues that lead to post-etch corrosion problems in NiFe and NiFeCo. However, the concentration of these residues may be significantly reduced by in-situ H2 or O2 plasma cleaning prior to removal of the samples from the etch reactor. [ABSTRACT FROM AUTHOR]