Saturation Magnetostriction Constant Research Articles

Magneto-Mechanical Coupling Study of Magnetorheological Elastomer Thin Films for Sensitivity Enhancement.

Magnetorheological elastomer thin films (MREFs) exhibit remarkable deformability and an adjustable modulus under magnetic fields, rendering them promising in fields such as robotics, flexible sensors, and biomedical engineering. Here, we fabricated MREF by introducing magnetostrictive particles (MSPs) and evaluated the magneto-mechanical coupling effect on the enhancement of sensitivity. The saturation magnetization (Ms) in a parallel anisotropic TbDyFe-PDMS MREF was 5.8 emu/g, and the initial tensile modulus was 55% greater than that of an Iso MREF. We propose a nonlinear magnetorheological formula on the magnetostriction effect, incorporating magnetic dipole interactions and the nonlinear prestress of magnetic particles. This formula highlights the complex nonlinear relationship between the external magnetic field (H) and the key parameters that affect the enhanced MR effect of MSPs-MREF, such as saturation magnetization, remanence (Mr), magnetostriction constant (λs) and stress deviator in ferromagnetic particles (Sed) in the magnetic chain structure. Furthermore, we validate the influence of the key parameters of the rectified magnetorheological formula on a nonlinear magneto-mechanical behavior of MSPs-MREF in PDMS-based MSPs-MREF models by using finite-element simulations. Finally, we developed a biosensor based on MSPs-MREF to detect human serum albumin at low concentrations in human urine samples. There is a 4-fold increase in sensitivity, a lower detection of limit (0.442 μg/mL), and a faster response time (15 min) than traditional biosensors, which in the future might provide an effective way of detecting biomolecules of low concentrations.

Comparative study of the giant stress impedance behavior of commercial amorphous ribbons for strain sensing applications

The giant magnetoimpedance (GMI) and giant stress impedance (GSI) behaviors of amorphous ribbons composed of three commercially available materials (Co66Si15B14Fe4Ni1, Fe81B13Si3.5C2, and Ni40Fe40Si + B19Mo1−2) with differing saturation magnetostriction constants (λs) and Young's moduli (E) were studied under longitudinal stress/strain. The linearity of the ribbons' GSI responses and gauge factors was measured to create a figure of merit and compare their stress/strain sensing performance for strains up to ɛ = 10 × 10−3. We observed that the Ni40Fe40Si + B19Mo1−2 ribbon displayed the best performance for low strains (ɛ < 1 × 10−3), whereas the Co66Si15B14Fe4Ni1 ribbon displayed the best performance for higher strains (ɛ < 10 × 10−3). We conclude that the suitability of a material for sensing strains in any given strain regime has a complex dependence on both λs and E, the former of which dictates both the absolute magnitude of the impedance variation materials exhibit (i.e., the dynamic range), while both λs and E control how their impedances vary with applied strain.

Investigation of Cu/NiFe composite wires by SAMR method

Composite Cu/NiFe wires with two different compositions of electrolytic NiFe layers were investigated by the small angle magnetization rotation (SAMR) method. From the measurements the induced anisotropy and the saturation magnetostriction constants were determined. The measurements were compared with the theoretical model based on the quasistatic approximation. The experimental results well agreed with the theory.

High-frequency power loss mechanisms in ultra-thin amorphous ribbons

Soft magnetic amorphous materials with ultra-low power loss are highly desirable for high-frequency drive applications. The present work demonstrates the high-frequency power loss performance and underlying loss mechanisms in ultra-thin amorphous alloys. This is achieved by rapid-quenching amorphous alloys of Co-, CoFe- and Fe-rich systems, investigating their amorphous atomic structure, quantifying the saturation magnetostriction constants (λs), imaging magnetic domains at remanent magnetization, analyzing magnetization reversal from various magnetization levels, and finally, investigating the material loss performance over a broad frequency range (f = 50 kHz–2 MHz) at various excitation levels (Bm = 25–100 mT). The ultra-high performance of ultra-thin Co-rich amorphous ribbons, as compared to CoFe- and Fe-rich alloys, was attributed to the significantly low eddy current loss, due to the reduced thickness, and a minimal amount of excess loss, owning to minimal magnetoelastic contributions and magnetization reversal by rotation. The underlying loss mechanisms were analyzed by decomposing material loss into primary components and identifying the magnetization reversal mechanisms using minor hysteresis loops. In the Co-rich amorphous alloys, we suggest that magnetization reversal by rotation dominates, at least at low excitations, while in CoFe- and Fe-rich alloys domain wall displacement prevails and contributes significantly to the excess loss up to the MHz frequency range. Magnetization reversal by rotation in Co-rich alloys could be attributed to the zero/near-zero λs, and eventually low residual stress, leading to a homogeneous magnetic domain structure, as compared to the inhomogeneous “fingerprint-like” complex domains in highly magnetostrictive CoFe-rich alloys.

Determination of saturation magnetostriction of amorphous Fe-Co-P-B ribbons: comparison of various methods

We present and compare results of measurement of saturation magnetostriction constants of amorphous ribbons Fe80-xCoxP14B6 (x = 23, 25, 28, 32, 40 at.%) and the reference Fe40Ni40P14B6 specimen employing Narita and Becker-Kersten methods. We also modified a strain gauge-based method to enable measurements of complete magnetic field dependence of magnetostriction coefficients.

Soft Magnetism, Magnetostriction, and Microwave Properties of Fe-Ga-C Alloy Films

A systematic investigation of the soft magnetism, the change of modulus of elasticity with magnetization (ΔE effect), magnetostriction, and microwave properties has been carried out on iron-gallium-carbon thin films over a wide carbon content range. The phase transformation of the Fe-Ga-C films from bcc polycrystalline to amorphous leads to excellent magnetic softness with a low coercivity of less than 1 Oe, high saturation magnetization, narrow ferromagnetic resonance linewidth at 10 GHz of 20 to 30 Oe, and an ultra-low Gilbert damping constant of 0.0027. A record high piezomagnetic coefficient of 9.71 ppm/Oe, high saturation magnetostriction constant of 81.2 ppm, and large ΔE effect of -120 GPa at 500 nm were achieved.

Atom probe analysis and magnetic properties of nanocrystalline Fe84.3Si4B8P3Cu0.7

We have investigated the microstructure and the magnetic properties of as-cast and flash annealed (4 s at 420 °C–560 °C) Fe84.3Si4B8P3Cu0.7 melt-spun ribbons. The scanning electron microscopy-electron backscattered diffraction (SEM-EBSD) analyses proved the existence of crystalline layer with the thickness of 1 μm in the as-cast state on both the wheel-contacted and the free surfaces of ribbons. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) patterns showed that the crystalline surfaces were textured. Moreover, the microstructure, composition and phase evolution of surface crystallization were studied using TEM and 3DAP which the spherulitic microstructure on the surface was demonstrated. Flash annealing above 420 °C led to a nanocrystalline microstructure of containing 10–15 nm α-Fe (Si) crystallites embedded in a residual amorphous matrix containing Fe, Si, B and P. Three-dimensional atom probe (3DAP) and high resolution transmission electron microscopy (HRTEM) analysis revealed that boron and phosphorous were rejected from α-Fe (Si) phase and enriched in the residual amorphous phase. The nucleation of the nanocrystals occurs heterogeneously from the 3–5 nm α-Fe crystals that were present in the as-cast state. The saturation magnetic induction (Bs) increases from Bs = 1.55 T in the amorphous state to Bs = 1.76 T after the crystallization. The saturation magnetostriction constant, λs, decreased from originally 35 ppm in the as-cast state to about 14 ppm with coercive fields in the range of Hc = 20–30 A/m.

Co-Based Amorphous Material for Giant Magnetoimpedance and Fluxgate Sensing Cores

Soft magnetic materials rich on iron or cobalt have found vast range of usability for sensors such as fluxgates [1] and also, the recently re-invented, magneto-impedance sensors [2]. Giant magneto-impedance (GMI) has experienced huge increase of interest since the late 80's. Although the fluxgate sensor is commercially available, the easy manufacturing of GMI sensors, possibility of miniaturization put attention to many scientists for developing such sensor in many applications. However, GMI sensor has major drawback of large temperature sensitivity [3]. In precise applications, fluxgate sensors are preferred over GMI, which do not saturate the ferromagnetic core and therefore may exhibit perming error. On the other side, the GMI sensors compete with significantly longer period of the development of fluxgates and recently are commercially used for evaluation of microstructural degradation in ferromagnetic materials [4]. Mostly for GMI sensors, amorphous/ nanostructured wires are used rather than ribbons as wire shaped sample has better GMI characteristics than ribbon [5] due to the formation of circumferential anisotropy in wire. On the other hand wires can be used for orthogonal fluxgates but ribbons are preferred over wires for commercial use as they have been tested for last few decades. The magnetization process for the ribbon and the wire shaped samples are assumed to be different presumably due to the difference in cooling process. However, in both cases, the materials should have very low saturation magnetostriction constant and high permeability. The present paper is to understand the variation of sensing properties of the ribbon and wire shaped materials having the same composition, which can be operated both in the GMI and the fluxgate sensing cores and test them in both sensors.

High Temperature Properties of CoFe/CoNi and Fe/CoNi Biphase Microwires

The objective of this work has been to analyze the high-temperature behavior of magnetically single-and biphase microwires because of its interest from fundamental and applications viewpoints. Two alloy compositions with amorphous structure covered by glass have been prepared as magnetically single phase microwires by quenching & drawing technique: CoFe-based with near zero saturation magnetostriction constant and Fe-based with positive saturation magnetostriction constant. The same wires were used as the core for magnetically biphase microwires. Second CoNi phase was deposited by electroplating. Magnitudes as saturation magnetization and hysteresis parameters are determined in the temperature range from room temperature up to 1200 K. We proceed to a comparative analysis of their magnetic behaviour at different temperatures as well as after cooling down to room temperature. Information on the Curie temperature of different phases and on the influence of heating process on the magnetic properties is thus derived.

Experimental determination of magnetocrystalline anisotropy constants and saturation magnetostriction constants of NiZn and NiZnCo ferrites intended to be used for antennas miniaturization

Abstract This study investigates the magnetocrystalline anisotropy constants (K 1 ) and the saturation magnetostriction constants ( λ S ) of Ni 1− x Zn x Fe 2 O 4 (NiZn) and Ni 0.8− x Zn x Co 0.2 Fe 1.98 O 4−δ (NiZnCo) ferrites intended to be used for antenna downsizing. Composite materials constituted of soft ferrite nanosized particles (NiZn or NiZnCo ferrites) embedded in an epoxy matrix are realized. Measurements of their magnetic permeability in the frequency range of 200 MHz–6 GHz are performed. The influence of compressive stress (in the range of 32–96 MPa) on their Ferrimagnetic Resonance (FMR) is demonstrated. An analytical modeling of stress-induced FMR changes is proposed that allows simultaneous determinations of the Natural Ferrimagnetic Resonance (NFMR, F 0 ), K 1 and λ S of Ni 1− x Zn x Fe 2 O 4 and Ni 0.8− x Zn x Co 0.2 Fe 1.98 O 4−δ ferrites. The obtained results for NiZn ferrites are in agreement with literature data, validating both the experimental process and the proposed modeling of the stress-induced FMR changes. Regarding NiZnCo ferrites, extended data on K 1 and λ S are presented for the first time. Increasing zinc content (x) induces a spin disorder that reduces in a same time K 1 and the magnetization at saturation M S . The rapid variation of K 1 (x) is related to that of the magnetization M S (x) through a power law. The single-ion anisotropy model allows a satisfactory interpretation of K 1 dependence on zinc content. The unexpected low values of λ S got for NiZnCo ferrites, compared to those got for NiZn ferrites, are also discussed. Application of compressive stress lowers noticeably magnetic losses of Ni 0.6 Zn 0.2 Co 0.2 Fe 1.98 O 4−δ at given frequency, thereby enhancing the ability of this spinel ferrite to be used as a substrate in the aim of antenna miniaturization.

A Low-Noise Fundamental-Mode Orthogonal Fluxgate Magnetometer

We introduce a low-noise fundamental-mode orthogonal fluxgate magnetometer for use in magnetotelluric surveys. The fluxgate makes use of rapidly quenched amorphous wire having vanishing value of saturation magnetostriction constant (λ ≈ 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> ) and displaying ultrasoft magnetic behavior. The design of the fluxgate consists of multiple U-shaped sensor heads where pairs of wire pieces are inserted as core material. The novelty of this system resides in the use of a quadruple sensor head. Digital signal processing with effective electronic noise suppression allows this magnetometer to achieve a noise floor of 0.8 pT/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> for frequencies above 10 Hz. The possibilities of in situ application are discussed and guidelines on noise suppression strategies are given.

Relationship Between the Temperature Changes of the Magnetostriction Constant and the Impedance of Amorphous Elastically Deformed Soft Magnetic Cobalt-Based Ribbons

The influence of the temperature on the impedance of amorphous soft magnetic low striction ribbons based on cobalt alloys is investigated. It is revealed that ribbon strain causes a significant increase in the sensitivity of the impedance to temperature changes. It is demonstrated that the given phenomenon is due to the temperature change of the saturation magnetostriction constant.

Effect of the Ni81Fe19 thickness on the magnetic properties of Ni81Fe19/Fe50Co50 bilayers

The effect of the Ni81Fe19 layer thickness on the magnetic and microstructural properties of Ni81Fe19/Fe50Co50 bilayers has been studied. The thickness of the Fe50Co50 layer was held constant at 15nm, while the Ni81Fe19 layer thickness increased from 15nm to 90nm. This meant that the Fe50Co50 layer plus the top of the Ni81Fe19 layer were measured using a magneto-optic Kerr effect magnetometer as the laser skin depth is of the order of 20nm. It was found that as the Ni81Fe19 layer increased in thickness the coercive and saturation fields of the bilayer structure decreased, while the effective saturation magnetostriction constant increased, towards the Fe50Co50 bulk effective saturation magnetostriction value.

Temperature Dependences of Magnetoimpedance of Nanocrystalline Fe-Based Ribbons

The influence of a magnetic field or the mechanical stresses on the impedance of the Fe73.5Si16.5B6Nb3Cu1 and Fe73.5Si13.5B9Nb3Cu1 ribbons was investigated in the (297 divided by 433) K temperature range. It is shown that impedance changes, which are observed under the application of mechanical stresses and temperature, are conditioned by the structural features and magnetic properties of the alloys. The temperature increase leads to a decrease of the saturation magnetostriction constant, an increase of the anisotropy axis dispersion and a decrease of the anisotropy effective value. It was determined that the maximum sensitivity of impedance to the mechanical stresses reaches the value of about 2%/MPa for the Fe73.5Si16.5B6Nb3Cu1 and Fe73.5Si13.5B9Nb3Cu1 samples.

An investigation of the effect of structural order on magnetostriction and magnetic behavior of Fe–Ga alloy thin films

This paper reports results from a comprehensive study of Fe–Ga films fabricated over a wide range of growth conditions. Polycrystalline Fe 100− x Ga x films (14 ⩽ x ⩽ 32) were deposited (using three different combinations of growth parameters) on Si(1 0 0) using a co-sputtering and evaporation technique. The growth parameters (sputter power, Ga evaporation rate and chamber pressure) were used primarily to control the Fe:Ga ratio in the films. X-ray diffraction showed that all films had 〈1 1 0〉 crystallographic texture normal to the film plane. The lattice parameter increased with % Ga up to x = 22 and was independent of growth parameters. Conversion electron Mössbauer spectroscopy studies showed a predominance of the disordered A2 phase in all films. It appears that the use of vacuum deposition with appropriate parameters can effectively suppress the D0 3 ordered phase. Systematic studies of the effective magnetostriction constant as a function of composition support this conclusion. It was found that films of high effective saturation magnetostriction constant and low stress could be fabricated using low Ar pressure, irrespective of sputter power or evaporation rate, giving properties useful for application in microelectromechanical systems.

Influence of Co content and thermal annealing on structural, magnetic and magneto elastic properties of nanocrystalline Fe–Co–Nb–B alloys

Structural, magnetic and magneto elastic properties of the nanocrystalline Fe 84- x Co x Nb 7B 9 ( x=17, 25, 33) alloys have been studied using differential scanning calorimetry, X-ray diffraction, hysteresis and magnetostrictive measurements. Successive addition of Co reduces the stability of the alloys against the crystallization and also affects the structural, magnetic and magneto elastic properties. Observed magnetic behaviour suggests that in the coercive field exhibits for the increase of Co content in the alloy there is a changeover from third power dependence to sixth power dependence on grain size, ascribed to the presence of annealing induced anisotropies. Both experimentally obtained and estimated values of the saturation magnetostriction constant shows noticeable changes with increase in the annealing temperature and Co content in the parent alloy due to the increase of volume fraction of the nanograins, stresses and grain growth. Co content in nanocrystalline bcc Fe–Co phase ranges between 10–66%; whereas volume fraction of nanocrystalline phase and average grain diameter is in the range 15–70% and 8–20 nm, respectively.

Effect of Stress Annealing on the Saturation Magnetostriction of Nanocrystalline Fe$_{73.5}$Cu$_{1}$Nb$_{3}$Si$_{15.5}$B$_{7}$

Ribbons of amorphous Fe73.5Cu1Nb3Si15.5B7 have been crystallized by annealing under tensile stress. As typical for this composition, the annealed ribbons reveal a nanocrystalline structure with low coercivity, near-zero magnetostriction, and a strong creep-induced anisotropy proportional to the annealing stress. The present work shows that the tensile stress, ?a, applied during annealing also affects the saturation magnetostriction ?s. Accordingly, ?sdecreases linearly with increasing magnitude of ?a. The samples have an initially small positive magnetostriction and, hence, ?s even changes its sign from positive to negative with increasing annealing stress. This change of sign provides qualitative evidence that the effect is clearly beyond experimental error. Our finding is compared to the elastic stress dependence of the saturation magnetostriction constant. The latter is a well-established phenomena for amorphous Co-base alloys and, as we will demonstrate, can also be observed in nanocrystalline alloys. The results will be discussed theoretically in terms of the strain dependence of the magnetic anisotropy energy which ultimately provides the physical origin of magnetostrictive phenomena.

Giant Electric Field Tuning of Magnetism in Novel Multiferroic FeGaB/Lead Zinc Niobate–Lead Titanate (PZN‐PT) Heterostructures

Multiferroic composite materials consisting of both a magnetic phase and a ferroelectric phase are of great current interest, as they offer the possibility ofmagnetoelectric (ME) coupling, that is, electric field manipulation of magnetic properties (converse ME effect) or vice versa (direct ME effect), and have led to many novel multiferroic devices. One important series of such multiferroic devices is constituted by electrostatically tunable microwave multiferroic signal processing devices, including tunable resonators, phase shifters, and tunable filters. Compared to conventional tunable microwave magnetic devices, which are tuned by magnetic fields, these electrostatically tunable microwave multiferroic devices are much more energy efficient, less noisy, compact, and lightweight. ME effects can be realized in multiferroic composites through a strain/stress-mediated interaction, which enables effective energy transfer between electric and magnetic fields and leads to important new functionalities and devices. Strong ME coupling is critical for multiferroic devices; however, it has been difficult to achieve at microwave frequencies, leading to a very limited tunability in electrostatically tunable microwave multiferroic devices. The demonstrated tunable range of most of these devices has been very limited, with a frequency tunability of Df< 150MHz and a low tunable magnetic field of DH< 50Oe (1 Oe 79.6 A m ). This is mainly due to the large loss tangents at microwave frequencies of the two constituent phases, that is, the ferroelectric phase and, particularly, the magnetic phase, which is less resistive. The ME coupling strength in multiferroic composites is determined by many factors, such as the properties of the two constituent phases, the interface between them, the mode of ME coupling, and the orientation of the magnetic and electric fields. As a result, layered multiferroic heterostructures with magnetic thin films provide great opportunities for achieving strong ME coupling at microwave frequencies, owing to minimized charge leakage paths and low loss tangents associated with magnetic thin films. It is also desirable for the magnetic phase in the multiferroic composites to have a narrow ferromagnetic resonance (FMR) linewidth and a large piezomagnetic coefficient (dl/dH), that is, a large saturation magnetostriction constant (ls) and a low saturation magnetic field (Hs). However, suchmagnetic materials have not been readily available. Very recently, we have reported a new class of metallic magnetic FeGaB films that has a high ls of ca. 70 ppm, a lowHs of ca. 20Oe, and a narrow FMR linewidth of ca. 16Oe at X-band (ca. 9.6GHz). The maximum piezomagnetic coefficient of the FeGaB films is about 7 ppm Oe , which is much higher than those of other well-known magnetostrictive materials used in multiferroic composites, such as Terfenol-D (Tb-Dy-Fe), Galfenol (Fe-Ga), and Metglas (FeBSiC), as shown in Figure 1. The combination of narrow FMR linewidth and high piezomagnetic coefficient makes these FeGaB films excellent candidates for the magnetic material in microwave multiferroic composites. Single-crystal ferroelectrics such as lead magnesium niobate–lead titanate (PMN-PT) and lead zinc niobate–lead titanate (PZN-PT) having giant piezoelectric coefficients and low loss tangents are desired for microwave multiferroic composites as well. In particular, (011)-cut PMN-PT and PZN-PT single-crystal slabs have anisotropic piezoelectric coefficients d31 and d32 when poled along their [011] crystalline direction. For example, (011)-cut PZN-PT single crystals with 6% lead titanate have high anisotropic piezoelectric coefficients d311⁄4 3000 pC N 1 and d321⁄4 1100 pC N . The giant anisotropic piezoelectric coefficients of the PZN-PTsingle crystal provide great opportunities for generating a large in-plane magnetic anisotropic field and

Structure, magnetic and magnetostrictive properties of as-deposited Fe–Ga thin films

Polycrystalline Fe 100− x Ga x (19⩽ x⩽23) films were grown on Si(1 0 0) substrates at different partial pressures of sputtering gas ranging from 3 to 7 μbar. Microstructural, magnetic and magnetostrictive properties were studied using X-ray diffraction (XRD), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS) and magneto-optic Kerr effect (MOKE) magnetometry respectively. X-ray diffraction showed that all films have the body-centered cubic (bcc) Fe–Ga phase with the 〈1 1 0〉 direction out of the film plane. Magnetic characterization of the films showed that the films prepared at 3 μbar had weak uniaxial anisotropy whereas films grown at Ar pressures in the range 4–7 μbar were magnetically isotropic. The effective saturation magnetostriction constants ( λ eff ) of the films were measured using the Villari effect. It was found that effective saturation magnetostriction constants were almost constant over the Ga composition range achieved by varying the sputtering pressure. The measured effective magnetostriction constants fit closely to the calculated saturation magnetostriction constants of 〈1 1 0〉 textured polycrystalline films with the 〈1 1 0〉 directions slightly canted with respect to the normal to the sample surface. It was found that a high pressure of the sputtering gas effected the magnetic softness of the films. The saturation field increased and remanence ratio decreased with increase in pressure.

The influence of substrate on the magnetic properties of MnZn ferrite thin film fabricated by alternate sputtering

Mn0.5Zn0.5Fe2O4 film which has the highest saturation magnetization among Mn1–x Znx Fe2O4 thin films was prepared by the alternate rf sputtering method from two targets with compositions of MnFe2O4 and ZnFe2O4, respectively. The films were deposited on single-crystal Si(100), MgO(100) and SiO2/Si(100) substrates. The as-deposited films were amorphous, and after annealing in a vacuum furnace at 550 °C, polycrystalline MnZn ferrite films with residual amorphous matrix were obtained. The coercivity of all films is low, and the film on the MgO(100) substrate shows a coercivity as low as 27 Oe. The grain size of all films is about 20 nm and is less than the ferromagnetic exchange length (160 nm), so magnetic anisotropies are averaged to lower effective values. Furthermore, the negative magnetostriction constant of crystalline MnZn ferrite and the positive magnetostriction constant of amorphous Fe-based matrix will cancel out and may lead to a low or vanishing saturation magnetostriction constant. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)