In-plane Magnetic Properties Research Articles

Magnetic field sensing elements based on Ni80Fe20 2D magnetoplasmonic crystals

Here we demonstrate the fabrication of magnetic field sensing elements based on 2D magnetoplasmonic crystals prepared using e-beam lithography and magnetron sputtering methods. The magnetoplasmonic crystals consist of square lattice diffraction gratings with varying filling factors layered with Ag, Ni80Fe20, and Si3N4 layers. Based on the magnetic, optical, and magneto-optical studies, the magnetoplasmonic crystal that allows for both high transverse Kerr effect and isotropic in-plane magnetic properties along the diffraction grating vectors was determined. The sensitivity and measuring range of this sample provide a perspective for measuring several components of an external magnetic field.

In-plane magnetic properties and anisotropy of scandium substituted thulium iron garnet thin films for fluxgate magnetometer

In-plane easily magnetized scandium substituted thulium iron garnet films(Tm3Fe5-xScxO12) with soft magnetic properties have recently attracted attention for fluxgate magnetometer applications. In this paper, thin Tm3Fe5-xScxO12 films were prepared on gadolinium gallium garnet substrates by liquid phase epitaxial(LPE) method. Microstructural properties, composition, magnetic properties and the in-plane anisotropy of the films were discussed. We found that the films turned from tensile stress to compressive stress as the Sc3+ substitution decreased, and the in-plane anisotropy was mainly caused by stress reducing as Sc3+ declined. By analyzing the in-plane magnetic hysteresis loops, the magnetic performance was the best when x = 0.75. Tm3Fe4.25Sc0.75O12 film had the lowest in-plane coercive field(0.006 Oe) and the highest initial magnetic permeability(378), which was more beneficial to realize fluxgate magnetometers.

Magnetic Properties of Amorphous Ta/CoFeB/MgO/Ta Thin Films on Deformable Substrates with Magnetic Field Angle and Tensile Strain.

Recently, the application of cobalt iron boron (CoFeB) thin films in magnetic sensors has been widely studied owing to their high magnetic moment, anisotropy, and stability. However, most of these studies were conducted on rigid silicon substrates. For diverse applications of magnetic and angle sensors, it is important to explore the properties of ferromagnetic thin films grown on nonrigid deformable substrates. In this study, representative deformable substrates (polyimide (PI), polyethylene naphthalate (PEN), and polydimethylsiloxane (PDMS)), which can be bent or stretched, were used to assess the in-plane magnetic field angle-dependent properties of amorphous Ta/CoFeB/MgO/Ta thin films grown on deformable substrates. The effects of substrate roughness, tensile stress, deformable substrate characteristics, and sputtering on magnetic properties, such as the coercive field (Hc), remanence over saturation magnetization (Mr/Ms), and biaxial characteristics, were investigated. This study presents an unconventional foundation for exploring deformable magnetic sensors capable of detecting magnetic field angles.

A in-plane biaxial strain tunable electronic structures and magnetic properties of Fe2C monolayer

This work intends to study the effect of a in-plane biaxial strain (ε) on the electronic structures and magnetic properties of monolayer Fe2C by first-principles calculation. The unstrained and strained Fe2C monolayer is thermally, dynamically, and mechanically stable, and unstrained Fe2C monolayer is ferromagnetic metal with the Curie temperature (TC) of 510 K. Introducing the tensile strain, the magnetic moments, spin polarization and magnetic anisotropy energy (MAE) can be significantly enhanced. Furthermore, a phase transition from ferromagnetic to antiferromagnetic ordering occurs at the ε of 12%, −10%. Especially, the result of Monte Carlo simulations demonstrates that the TC decreases with strain and Néel temperature TN increases with the tensile strain. A tensile strain applied on Fe2C monolayer with the value less than 8% facilitates the enhancement of MAE and spin polarization, and maintaining the TC above room temperature. This study provides a theoretical guide for the application of monolayer Fe2C in spintronic devices, and provides a basis for tuning the physical properties to two-dimensional MXene materials.

Integration of epitaxial La2/3Sr1/3MnO3 thin films on silicon-on-sapphire substrate for MEMS applications

We report the integration of high-quality epitaxial La2/3Sr1/3MnO3 (LSMO) thin films onto SrTiO3 buffered Silicon-on-Sapphire (SOS) substrates by combining state-of-the-art thin film growth techniques such as molecular beam epitaxy and pulsed laser deposition. Detailed structural, magnetic and electrical characterizations of the LSMO/STO/SOS heterostructures show that the LSMO film properties are competitive with those directly grown on oxide substrates. X-ray magnetic circular dichroism measurements on Mn L2,3 edges show strong dichroic signal at room temperature, and angular-dependent in-plane magnetic properties by magneto-optical Kerr magnetometry reveal isotropic magnetic anisotropy. Suspended micro-bridges were thus finally fabricated by silicon micromachining, thus demonstrating the potential use of integrating LSMO magnetic layer on industrially compatible SOS substrates for the development of applicative MEMS devices.

Crystalline orientation-related magnetic anisotropy in transition metal dichalcogenides 1T′-MoTe2/Co heterostructures

The semimetal transition metal dichalcogenides (TMD) MoTe2 have attracted extensive research interests in Spintronics. The understanding of the magnetic properties of MoTe2/Ferromagnetic (FM) heterostructures is critical to the design of novel Spintronics-based devices. However, there is lack of research on the magnetic anisotropy of the semimetal TMD/FM. Here, we demonstrate the in-plane crystalline orientation-related magnetic properties of MoTe2/Co to clarify the relationship between the crystalline orientation and the magnetic anisotropy. We carried out the studies of crystalline orientation-related magnetic anisotropy in 1T′-MoTe2/Co heterostructures from both experiments and first-principles calculations. Our results show that for Co with different thicknesses, the easy axis of Co film is along the b-axis of MoTe2 with uniaxial magnetic anisotropy. It is also consistent with the results of our theoretical results. When Co film thickness increases, the magnetocrystalline anisotropy (MCA) oscillates around a constant value with a lower MCA along the out-of-plane direction. Meanwhile, the demagnetization energy which increases linearly as a function of Co thickness, which would make the easy axis in-plane. Our work may give a fundamental inspiration for Spintronics based devices with semi-metallic TMDs/ferromagnetic materials.

Effect of Mo monoatomic interlayer on magnetic properties of in-plane anisotropic Nd-Fe-B/Mo/FeCo nanocomposite multilayered films

The Nd-Fe-B/Mo/Fe-Co multilayered films on MgO(001) were fabricated by UHV sputtering method. The as-deposited films showed soft magnetic properties with weak perpendicular magnetic anisotropy, and after annealing above 650°C, these films showed in-plane magnetic anisotropy, good squareness, and hard magnetic properties with high coercivity of about 8 kOe. The (220) peak of Nd2Fe14B was identified in the XRD pattern after annealing of the film, which means that the c-axis, which is the easy axis of magnetization, points in the plane of the film, consistent with the measurement of the magnetization curve. The positive peak of ΔM plot of in-plane direction of the film annealed at 800°C was shown. This result suggests existence of exchange coupling between the Nd-Fe-B and Fe-Co layers in the in-plane anisotropic multilayered film with monoatomic Mo interlayer.

Growth and characterization of La0.67Sr0.33MnO3/YBa2Cu3O7−δ bilayers

Understanding the interplay of ferromagnets and superconductors requires high quality interfaces. To this end, we have fabricated heterostructures of the cuprate superconductor YBa2Cu3O7−δ (YBCO) with the metallic ferromagnet La0.67Sr0.33MnO3 (LSMO) via pulsed laser deposition on SrTiO3 (STO) (001) and (LaAlO3)0.3(Sr2TaAlO6)0.7 (LSAT) (001) substrates. By varying the YBCO thickness from 1.7-13.6 nm while keeping the LSMO thickness at 12 nm, we have studied the interplay between ferromagnetism and superconductivity in the in-plane transport and magnetic properties of the bilayers. X-ray reflectivity data indicate the presence of a 2-3 nm thick interfacial layer between the LSMO and YBCO layers in all heterostructures. In-plane transport measurements exhibit suppression of the superconducting transition temperature from bulk YBCO values. Magnetometry measurements indicate high LSMO saturation magnetization values for samples grown on STO substrates and even higher (bulk-like) magnetization for bilayers grown on LSAT substrates. Together these results indicate that the interdiffused layer is largely attributed to a modified YBCO layer.

Effects of cathode rotation and substrate materials on electrodeposited CoMnP thick films

In this study, rotating-cathode electrodeposition was performed to deposit 30 μm thick CoMnP films on various substrate materials at room temperature. The electrodeposition configuration and parameters realized a constant current efficiency of about 95%, which was under activation control rather than mass-transport control. Compositional analysis indicated that the deposited thick films were Co-rich with a Co content 92–95 wt.%, regardless of deposition parameters. X-ray diffraction revealed that cathode rotation physically altered the preferred orientation of Co crystallites. The texture of Co crystallites changed with the cathode rotational speed from distinct hexagonal close-packed (HCP) (002) to a heterogeneous phase mixture of HCP (110) and face-centered cubic (FCC) (220). The substrate materials physicochemically affected the relationship between rotational speed and microstructural evolution. The microstructural texture changed nonlinearly with the cathode rotational speed when the films were deposited on catalytic substrate materials, suggesting a substantial influence of the substrate activation nature. Due to magnetocrystalline anisotropy, the resultant films exhibited hard magnetic properties while depositing at the optimal cathode rotational speed. Stationary-cathode electrodeposition resulted in rough CoMnP films with Co grains of 8–18 nm and high Mn content. These films exhibited unique in-plane magnetic properties compared with the films deposited with electrolyte agitation. This study is the first to investigate the combined effects of cathode rotational speed and the activation nature of substrates on the growth behavior of electrodeposited Co-rich CoMnP thick films. The results can be extended to electrodeposition of other Co-based alloys, such as CoP, CoNiP, CoWP, CoPtP, and CoNiMnP.

Magnetic and electric properties of single crystal MnI2

Multiferroic materials endowed with both dielectric and magnetic orders, are ideal candidates for a wide range of applications. In this work, we reported two phase transitions of MnI2 at 3.45 K and 4 K by systemically measuring the magnetic-field and temperature-dependent magnetization of the MnI2 thin flakes. Furthermore, we observed similar temperature and field-dependent behaviours for the magnetic susceptibility of MnI2 and electronic capacitance of the Ag/MnI2/Ag devices below 3.5 K. Considering the related theory work, we discussed the relationship between the antiferromagnetic and ferroelectric orders in MnI2. Our work reveals the in-plane magnetic and electric properties of MnI2 materials, which might be helpful for the further investigation and application of MnI2 multiferroics in the future.

Elastic strain control of electronic structure, and magnetic properties of [Pr1−xCaxMnO3/SrTiO3]15 superlattices

We report the growth, electronic structure, and in-plane magnetic properties of pulsed laser deposition grown 2D superlattice structures [Pr0.7Ca0.3MnO3/SrTiO3]15 and [Pr0.5Ca0.5MnO3/SrTiO3]15 on (001) oriented SrTiO3 and LaAlO3 single crystal substrates. The x-ray reflectivity measurements reveal well-defined interfaces between the manganite and titanate layers along with the existence of Kiessig fringes, providing the evidence for the smooth periodic superlattice structure. The reciprocal space mapping provides signature of tetragonal distortion in all the superlattices. The electronic structure determined from the x-ray photoelectron spectroscopy reveals divalent Sr and Ca, tetravalent Ti, and mixed valent Mn with a pronounce shift of binding energy peaks toward the higher energy side in the superlattices grown on (001) oriented LaAlO3 as compared to those grown on SrTiO3. These superlattices exhibit highly anisotropic ferromagnetic character. We used the law of approach to saturation to determine the anisotropy field (HK) and cubic anisotropy constant (K1) for all the investigated superlattices. This analysis yields the highest HK∼9 kOe and K1∼8×105 erg/cc for the [Pr0.7Ca0.3MnO3/SrTiO3]15 superlattice system. Furthermore, significant enhancement of the overall magnetic moment and a decrease in TC (<100 K) was observed in the case of LaAlO3 grown superlattice, which indicates a substantial role of residual elastic strain on the magnetic ordering. Our results indicate that the strain induced elongation of MnO6 octahedra leads to finite possibility of non-orthogonal overlapping of orbitals in the presence of large crystal field splitting of eg levels, which, in turn, causes suppression of the ferromagnetic double exchange interaction.

Observation of unexpected uniaxial magnetic anisotropy in La2/3Sr1/3MnO3 films by a BaTiO3 overlayer in an artificial multiferroic bilayer.

We studied in detail the in-plane magnetic properties of heterostructures based on a ferroelectric BaTiO3 overlayer deposited on a ferromagnetic La2/3Sr1/3MnO3 film grown epitaxially on pseudocubic (001)-oriented SrTiO3, (LaAlO3)0.3(Sr2TaAlO6)0.7 and LaAlO3 substrates. In this configuration, the combination of both functional perovskites constitutes an artificial multiferroic system with potential applications in spintronic devices based on the magnetoelectric effect. La2/3Sr1/3MnO3 single layers and BaTiO3/La2/3Sr1/3MnO3 bilayers using the pulsed-laser deposition technique. We analyzed the films structurally through X-ray reciprocal space maps and high-angle annular dark field microscopy, and magnetically via thermal demagnetization curves and in-plane magnetization versus applied magnetic field loops at room temperature. Our results indicate that the BaTiO3 layer induces an additional strain in the La2/3Sr1/3MnO3 layers close to their common interface. The presence of BaTiO3 on the surface of tensile-strained La2/3Sr1/3MnO3 films transforms the in-plane biaxial magnetic anisotropy present in the single layer into an in-plane uniaxial magnetic anisotropy. Our experimental evidence suggests that this change in the magnetic anisotropy only occurs in tensile-strained La2/3Sr1/3MnO3 film and is favored by an additional strain on the La2/3Sr1/3MnO3 layer promoted by the BaTiO3 film. These findings reveal an additional mechanism that alters the magnetic behavior of the ferromagnetic layer, and consequently, deserves further in-depth research to determine how it can modify the magnetoelectric coupling of this hybrid multiferroic system.

Ultrasound-assisted electroless deposition of Co-P hard magnetic films

We present here the growth kinetics and characterization of Co-P magnetic films deposited electrolessly from alkaline baths onto activated copper substrates with and without the assistance of an ultrasonic agitation (UsA). Regular electroless deposition was conducted at 60 °C, 68 °C, 76 °C and 84 °C, respectively. A 53 kHz ultrasound with an output power of 162 watt was adopted for a desired deposition rate at 44 °C, 52 °C and 60 °C, respectively. The deposition rates, for films deposited at 60 °C, are 53 and 21 nm/min, respectively, with and without UsA. The autocatalytic reaction follows a first order reaction mechanism for both regular and UsA-electroless deposition methods. Arrhenius analyses indicate that the activation energies are 34.7 kJ/mol and 83.8 kJ/mol, respectively, with and without UsA. Comparing films deposited to the same thickness of 1.1 μm, the films deposited with UsA at 60 °C exhibit magnetic properties comparable to those films deposited without ultrasound at temperatures higher than 80 °C. In the former case, the best in-plane hard magnetic properties are intrinsic coercivity (Hci) 620 Oe and residual magnetization (Mr) 114 emu/g. The perpendicular ones are Hci 1280 Oe and Mr 43 emu/g. The relationships among depositing reaction kinetics, film composition, morphology and crystal structure well explain the observed evolution of magnetic and mechanical properties. Comparing with the regular electroless deposition, UsA facilitates maintaining Co content, smoothening morphology and forming nano-crystalline grains, resulting in enhanced Hci, Mr and hardness at relatively lower depositing temperatures. The hard magnetic Co-P films produced by UsA-electroless deposition are promising for various applications such as micro-electromechanical systems (MEMS) and recording media.

Influence of crystal orientation on the magnetostriction behavior of Fe films formed on MgO single-crystal substrates

Abstract Fe thin films are prepared on MgO substrates of (001), (110), and (111) orientations by ultra-high vacuum magnetron sputtering. The magnetostriction behaviors under rotating magnetic fields are observed by using a cantilever method. The relationship between in-plane magnetic anisotropy and magnetostriction behavior is investigated. An Fe(001)bcc single-crystal film is obtained on MgO(001) substrate. A four-fold symmetry in in-plane magnetic anisotropy is observed for the Fe(001)bcc film, where the easy magnetization directions are parallel to bcc[100] and bcc[010]. An Fe(211)bcc bi-crystalline film is formed on MgO(110) substrate and the film also shows an almost four-fold symmetric magnetic anisotropy. The reason is interpreted to be due to an influence of overlap of magnetic anisotropies of two bcc(211) variants with two effective easy magnetization directions which are obtained by projecting bcc[010] and bcc[001] on the bcc(211) plane. An Fe(110)bcc film is epitaxially grown on MgO(111) substrate with two types of variant with the crystallographic orientation relationships similar to Nishiyama-Wasserman and Kurdjumov-Sachs. The Fe(110) film shows an isotropic in-plane magnetic property due to an influence of the variant structure. Usual sinusoidal waveforms of magnetostriction are observed for the Fe(110) film. On the other hand, waveforms measured for the Fe(001) and the Fe(211) films are deformed from sinusoidal shape under low in-plane rotating magnetic fields and the magnetostriction behaviors are similar between the two films. Rectangular waveforms are observed for the bending parallel to easy magnetization directions, whereas triangular waveforms are recognized for the bending parallel to hard directions. The phenomenon is related to the direction difference between applied magnetic field and magnetization in magnetically unsaturated films with in-plane anisotropies. The magnetostriction behavior is influenced by the symmetry of in-plane magnetic anisotropy.

A novel CoCuP electrodeposited film with improved planar hard magnetic properties and film quality

We designed to add Cu into Co-P hard magnetic films prepared via electroplating. The purpose was to make use of immiscibility between Co and Cu, hoping that Cu will segregate at Co-grain-boundaries to mediate magnetic decoupling. Copper is found very difficult to co-electrodeposit with Co due to the large difference in the reduction potentials. A slight variation of CuSO4 concentration in the electrolyte from 1 mM to 2 mM results in a big difference of Cu content from 3.8 wt% to 13 wt% in CoCuP films. However, the CoCuP films are amazingly crack-free up to a thickness no less than 6 μm. The films electroplated with CuSO4 concentration 1.3 mM at pH 4.7 and 25 °C have a Cu content 5.5 wt%, P content 3.1 wt% and exhibit the best magnetic properties. The in-plane magnetic properties are Hc 360 Oe, Br 7450 G, and (BH)m 1.21 MGOe. The perpendicular ones are Hc 800 Oe, Br 1600 G, and (BH)m 0.35 MGOe. The evolution in film composition, microstructure and crystal structure well explains the variation in resultant magnetic properties. These films are readily applicable in mini- and micro-devices which need in-plane magnetic performance.

Magnetic and structural anisotropic properties of magnetostrictive Fe-Ga flake particles and their epoxy-bonded composites

Flake shaped particles of grain-oriented Fe80Ga20 and Fe73Ga27 alloys were prepared using a high-energy wet ball-milling process. The surface of flakes produced were predominantly parallel to the (1 0 0) crystallographic plane in flakes. These flakes possess two in-plane 〈1 0 0〉 easy axes of magnetization, which enhances magnetostrictive performance and sensitivity for use in composite materials. The deformation mechanism leading to formation of (1 0 0) grain-oriented flakes is associated with small angel crystal reorientations along slip lines similar to what occurs during rolling. Data are presented on the in-plane magnetic properties of these flakes, which were characterized using field-dependent magnetization measurements. The epoxy-bonded composites with the particle alignment exhibited high magnetostriction values of ∼103 ppm.

Optimized microwave magnetic characteristics for patterned FeNi nanoparticle films manufactured by electric field-assisted deposition

The high-density FeNi nanoparticle films with strip structures were prepared by electric field-assisted deposition technique. The electric field of 10–40kV was applied on the sputtering platform during thin film deposition in order to obtain superior in-plane soft magnetic properties. The dependence of magnetic properties and microwave behavior on electric field was investigated. It is found that these high-density films have magnetically easy-modulated characteristics, especially for the strip-patterned ones. Application of electric field is very effective to obtain stronger in-plane magnetic anisotropy field and higher saturation magnetization simultaneously for our samples. In this case, large permeability and high ferromagnetic resonance frequency are easily achieved when the strip-patterned films are used in a wide gigahertz range. The experimental results indicate that electric field-assisted deposition technique is one of the important and promising manufacture methods to prepare thin film materials with enhanced gigahertz electromagnetic wave properties.

Improvement of microwave permeability spectra in high stacking density FeNi nanoparticle films prepared by electric field-assisted deposition

We proposed an advanced method to improve saturation magnetization of soft magnetic nanoparticle films, which are of great concern for application in modern electromagnetic devices operated in the GHz range. Fe50Ni50 nanoparticle films with a particle size of about 6 nm were fabricated at room temperature by electric field-assisted deposition. An electric field of 10–20 kV was applied on the deposition platform during the film’s manufacture to obtain high stacking density and superior in-plane soft magnetic properties in the films. Based on the results of the microwave permeability spectra, it is found that the samples with higher saturation magnetization have excellent microwave response. These results indicate that magnetic softness and microwave behavior of FeNi nanoparticle films can be modulated by applying electric field during deposition.

In-plane isotropic magnetic and electrical properties of MnAs/InAs/GaAs[formula omitted]B hybrid structure

We characterized in-plane magnetic and electrical properties of MnAs/InAs/GaAs(111)B hybrid structure grown by molecular beam epitaxy (MBE). We observed isotropic easy magnetization in two crystallographic in-plane directions, [2̅110] and [01̅10] of hexagonal MnAs i.e. [1̅10] and [112̅] of cubic InAs. We also fabricated transmission line model (TLM) devices, and observed almost isotropic electrical properties in two crystallographic in-plane directions, [1̅10] and [112̅] of cubic InAs. Also we tried to fabricate and characterize lateral spin-valve (LSV) devices from the hybrid structure. We could roughly estimate the spin injection efficiency and the spin diffusion length at room temperature in [112̅] direction. We believe that the hybrid structures are helpful to design spintronic device with good flexibility in-plane.

Enhanced In-Plane Anisotropy and Ferromagnetic Resonance Frequency in Permalloy Films Laminated With Nitrogen-Doped Tantalum

Soft magnetic materials are used in integrated power magnetic devices (such as micro-inductors and microtransformers) to achieve reasonable inductances at frequencies over a few megahertz. However, the out-of-plane (perpendicular) anisotropy, in thick films produced by vapor deposition, worsens the in-plane soft magnetic properties. This paper reports on the nano-lamination of Permalloy (Ni81Fe19) thin films with the introduction of nitrogen-doped tantalum in between to eliminate the out-of-plane anisotropy and improve the in-plane anisotropy. This significantly improves the in-plane soft magnetic properties, reducing the coercivity from 1352 A/m to 25.5 A/m and increasing the anisotropy field from 180 A/m to 660 A/m. The high-frequency permeability was uniform up to 500 MHz, and the ferromagnetic resonance (FMR) frequency was increased to 1 GHz. These properties are ideal for high efficiency magnetic applications at high frequencies and an extended FMR frequency is imperative for gigahertz-range devices.