Magnetic sensors are based on physical effects that relate an electrical resistance directly to an external magnetic field, namely the GMR and the tunneling magnetoresistance effect in ultrathin multilayered film Nanomaterials for Medical Applications, 2013Magnetic Sensors Principles and Applications☆P. Ripka, Arafat, in Reference Module in Materials Science and Materials Engineering, 201910 SummaryMagnetic sensors are used to detect magnetic fields and they are essential tool for many engineering applications. Based on the applications, many variations of magnetic sensors have developed which can be classified in few groups magnetic field sensors, magnetic position and distance sensors, magnetic proximity switches, magnetic force and torque sensors, magnetic flowmeters and current sensors. Each of the class has many variations of sensors. Magnetic sensors are being used in almost all engineering applications such as automobiles, military, robotics, medical devices, space equipment, geophysics and industrial full chapterURL sensors for assessing and monitoring civil Wang, G. Wang, in Sensor Technologies for Civil Infrastructures, Role of microstructure in magnetization and magnetoelasticityIn magnetoelastic stress sensors, magnetic relative permeability is used to reflect stress level in steel structures. Zero-stress saturated permeability permeability at technical magnetic saturation with no stress applied on the steel rod defines the stress-free status of the steel to be permeability implies the realigning tendency of magnetic domains in response to an exterior magnetic field. Metallurgical characteristics strongly influence magnetic permeability. The hardness represents the mechanical stiffness of the material and depends on multiple metallurgical characteristics, including composition, phase constitutes and morphology, residual stress, and grain size, etc. Those factors also play roles in pinning effects against magnetic domain reorientation. The correlation of hardness with permeability is demonstrated in Fig. and Table It can be seen that the harder the ferromagnetic steel, the lower the initiative permeability. There are several causes for this observation – I the amount of the ferrite phase decreases as carbon content increases, and ferrite is magnetically the softest microstructure in steel; II the carbides or other precipitates function as pinning particles against domain reorientation; III cold work, lattice defect, and even heat treatment and welding can introduce intrinsic residual stress, which decreases the initiative permeability due to the pinning effect; IV besides, specific intrinsic stresses lead to a certain level of magnetic anisotropy – one example is that in cold extruded steel rod, the longitudinal residual compressive stress introduces a magnetic anisotropy and a fictitious field;21 as another example, in material with non-zero magnetostriction, magnetization can be introduced on the cutting edge of the sample,31 owing to the influence of residual stress on magnetic moments and domains. This phenomenon can be used in NDE for geometric non-continuity in steels. Similar effects can be observed in The initiative magnetization curves of various Hardness of various carbon/alloy steels tested in Fig. HV at 500 g1018 cold drawn2178620 annealed2304140 annealed2401045 cold drawn331Piano steel wire467HV refers to hardness in indicated in Figs and the magnetic hysteresis and saturated permeability in steels depend on their relative heat treatments. The saturated permeability increases as hardness drops, with the exception of the as-received cold-drawn steel rod because of magnetic anisotropy caused by residual stress generated by cold drawing Hysteresis of piano steel having undergone different heat treatments; the hardness of the quenched, as-received, and normalized samples are respectively 740, 387, and 310 in Relative permeability of piano steels having undergone different heat treatments, measured in the descending stages of hysteresis. The hardness of the heat treated, as-received cold drawn, normalized, and annealed samples are respectively 740, 387, 310, and 210 in the EM stress sensor, relative incremental permeability under technical magnetic saturation is the parameter used for stress monitoring, as shown in Figs and Relative permeability measurements for piano steel during initial magnetization and magnetic hysteresis at various stress Relative permeability under technical saturation vs tension of different steel rods, tested under room temperature, permeability μ = ΔB/ μ0ΔH; μ0 relative permeability of the load well below elastic limit, magnetic permeability varies monotonically with tensile stress. When the tension increases beyond yielding point, the permeability first reaches its summit and then drops, as indicated in Fig. due to the collaborative effects of magnetoelasticity and metallurgical dislocation multiplication. Although the tensile stress tends to raise the relative permeability, the latter declines once the influence of multiplying dislocations takes the Permeability vs stress up to yield point for piano steel rod yielding point 1410 MPa tested at different working points in lieu of magnetic field.33Read full chapterURL production of sensors grown by MBEIchiro Shibasaki, Naohiro Kuze, in Molecular Beam Epitaxy, SummaryIn this chapter, we have discussed mass production of magnetic sensors and infrared sensors using narrow-bandgap compound semiconductor materials such as InSb, InAs and related antimonides grown by MBE. We showed that MBE system is suitable for the mass production of these sensors. Now Hall sensors produced by MBE are widely used for various electric apparatuses, mobile phones, digital cameras and automobile applications. Moreover, a miniaturised InSb photovoltaic infrared sensor operating at room temperature was demonstrated. The InSb photovoltaic infrared sensor was encapsulated in a very small package. The photocurrent of the infrared sensor showed good linear dependence on the irradiance power. The output voltage of InSb photovoltaic infrared sensor was proportional to the light absorbance of the active layer of the sensor and the energy difference between the emitter and the sensor. The InSb photovoltaic infrared sensor, with its high sensitivity, ease of manufacture and millimetre dimensions is a promising device for both noncontact thermometry and human body detection in portable device full chapterURL for aerial, automotive, and robotic applicationsIvan Petrunin, Gilbert Tang, in Advanced Sensor Technology, MagnetometersThe magnetometer, which can also be referred to as a magnetic sensor or compass, is a sensor for measuring the strength of the magnetic field as well as its direction. One of the most important applications of magnetometers is the measurement of the geomagnetic field that, after the transformation, provides information on the pose of a mobile system body in a form of an angle concerning the magnetic north of the Earth. Since this information can be obtained at any measurement step independently from the previous states of the mobile system, magnetometers play an important role in the inertial navigation system and are therefore present in virtually all mobile systems, where localization in any form might be types of magnetometers exist, which can be used for measurements of the magnetic field of low, medium, or high strength with representative boundaries between these categories 1 mGs or nT and 10 Gs 1 mT [80]. The most commonly used types of sensors are those based on the Hall effect and magnetoresistivity phenomenon. However, many other types of magnetometers exist [80] reflecting the long history of development and scientific and commercial applications. Three sensitivity grades can be also introduced high, medium, and low, and each of these can be found onboard an aerial, automotive, or robotic system. The typical applications for these three categories of magnetic sensors can be seen as follows Low sensitivity sensors are frequently used within the onboard electronic systems for noncontact switching and current sensing. Medium sensitivity sensors support magnetic direction finding most commonly as triaxial magnetometers within the inertial navigation system and mineral prospecting [81]. High sensitivity magnetic sensors commonly support magnetic field mapping [82], which finds applications in surveying, Earth and space exploration and navigation. The highest sensitivity so far can be achieved by using a so-called “quantum” magnetometer, where measurement is based on the interaction of atomic spins, such as from nitrogen-vacancy defect or atomic vapor cells and the atomic spins in the measurement medium [83]. The latest iterations of the quantum-based magnetometers can achieve a subnanotesla level of sensitivity. However, magnetic sensors of all kinds are sensitive to manmade interferences, such as that originating from electronic devices or power lines. Therefore special care should be taken when interpreting measurements from magnetometers as there is a chance that interference can lead to critical malfunction of the systems that rely on magnetic field measurements and consequent failures in the mobile platform operation. One of the examples of such a problem was illustrated in the recent report of a survey drone crash in the UK [84].Read full chapterURL interface circuits for sensorsF. Reverter, in Smart Sensors and Mems, Magnetic field measurementThe direct interface circuit shown in Fig. using μC 3 see Table was applied to measure the magnetic sensor indicated in Table Sifuentes et al., 2008; the other components of the circuit were Ri = 120 and Cd = μF. Figure shows the value of xR estimated by [ for magnetic fields between 75 μT and 600 μT generated by a current-controlled solenoid; in fact, the sensor could operate between − 600 μT and + 600 μT, but it was tested in a lower range due to limitations of the measurement set-up. The estimated xR was always positive and very small lower than but it agrees with the typical sensitivity of the sensor see Table According to the fitted straight line, the maximum non-linearity error was FSS, but this was mainly due to the non-linearity of the sensor see Table actually, when the circuit measured a bridge circuit emulated by resistors instead of the sensor, the maximum non-linearity error was about FSS. Therefore, the sensor – not the interface circuit, in spite of its simplicity – limited the accuracy of the measurement, as is to be expected from a well-designed interface circuit. On the other hand, assuming the overall measurement range, the effective resolution was about 7 bits which corresponds to 10 μT for a measuring time of about 50 ms required to average ten measurements. Note that for the same resolution in ohms , the resolution in bits here is smaller than that in Section since the overall change of resistance is smaller ± 6 according to Table Experimental results of the circuit in Fig. when measuring a magnetic full chapterURL GlassParmanand Sharma, Akihisa Inoue, in Handbook of Silicon Based MEMS Materials and Technologies, Tailorable Magnetic PropertiesIn addition to mechanical and chemical behavior, functional properties such as magnetism are also important for the fabrication of high-density memories, magnetic sensors, and magnetoelectronic and magneto-optic devices. Controlled growth and tailorable magnetic properties are required for the realization of these magnetic devices. Magnetic anisotropy and the Curie temperature Tc of a film are the key parameters, because the former governs the magnetization or spin direction, and the latter tells about the existence of spin ordering up to a particular temperature Tc. The ability to control magnetic anisotropy and Tc of a magnetic material is very much desirable from the application point of view. In general, the crystal structure of a material dictates its magnetic properties. As crystal structure is unique for a particular material, tailoring of magnetic properties is very difficult because they are dependent on the atomic positions, which are fixed by the crystal lattice. It is noticed that the small variations in atomic positions can result in a drastic change in magnetic properties or more precisely the magnetic anisotropy. The ideal situation for tailoring the magnetic properties of a material is to have the ability to change its interatomic distances. It is difficult in the case of crystalline materials, but it is possible for amorphous/glassy materials because their atoms are not bound to a particular order to demonstrate the tailorable magnetic properties of glassy thin films, Co–Fe–Ta–B glassy thin films were deposited and the effect of Zr dilution on magnetic and structural properties was studied [99, 100, 103]. The glassy Co–Fe–Ta–B films exhibit a very smooth surface Ra ∼ nm with a large value of ΔTx ∼41K region and high thermal stability of glassy phase. Deposited thin films ∼ μm at RT are magnetically soft Figure The magnetic domain state for the thin film is like a single domain Figure The thicker films have out-of-plane magnetization with a stripe domain structure at RT Figure Although the glassy state is not supposed to have anisotropy, short-range atomic ordering/stress can result in anisotropy. It was observed that the heat treatment is effective in removal of this anisotropy by relaxing the atomic a In-plane hysteresis loops measured at RT for the Co–Fe–Ta–B films of different thickness. Inset shows the variation in Hc, and Mr/Ms ratio with film thickness and the typical shape of the hysteresis loops observed for the thick films. b AFM topographic image, showing the typical surface of the films. c MFM image of film in virgin state. d–g MFM images of film after exposure to magnetic field d film e film f film g film Area of AFM and MFM images is 20 × 20 μm2.The Co–Fe–Ta–B glassy thin films of thickness less then μm have very different magnetic behavior at low temperature Figure The same film exhibiting stripe domain structure that is perpendicular magnetic anisotropy at room temperature exhibits an in-plane single-domain-like state at low temperature. This means that the magnetization direction changes from in-plane single-domain-like to out-of-plane multidomain with increasing temperature Figure c. This phenomenon is known as spin reorientation transition SRT, and is mostly observed in the case of ultrathin ferromagnetic multilayers consisting of few monolayers. In the case of glassy thin films SRT persists up to the thickness of ∼ μm [99, 100]. The value of SRT temperature TSRT in the as-deposited films strongly depends on the film thickness and the applied in-plane magnetic field during the measurements. The value of TSRT shifts towards the lower temperature with increasing film thickness and towards high temperatures with increasing in-plane magnetic field Figure b. The value of TSRT for a particular film thickness can be tailored by heat treatment, which causes an irreversible change in TSRT. After heat treatment TSRT shifts towards the higher temperature. The SRT observed in the present case is not governed by the temperature-dependent magnetocrystalline or interface anisotropy, which is supposed to be the main cause for SRT in ultrathin films. On the basis of our experimental results on the thick Co–Fe–Ta–B glassy films and the reported data on ultrathin films, it is concluded that the atomic randomness and the stresses are the main causes for the occurrence of SRT. It is worthwhile to point out that the SRT phenomenon was not observed in the case of bulk glassy alloy of similar composition. In addition to tailorable magnetic properties, these films are also mechanically a MT curves for Co–Fe–Ta–B films having different values of film thickness measured under an in-plane magnetic field of 10 Oe, b MT curves for film measured under different in-plane magnetic fields, and c in-plane hysteresis loops for film measured at different Co–Fe–Ta–B films remain amorphous by the dilution with Zr up to ∼ at.% [103]. However, the Curie temperature decreases linearly with an increase in Zr concentration. These results suggest that the magnetic properties such as magnetic anisotropy SRT and Tc can be tailored in case of glassy magnetic thin films and are quite promising for versatile magnetic manipulations and device full chapterURL and NanochemistryQ. Fang, ... G. Zhu, in Comprehensive Nanoscience and Technology, MagnetismMagnetism is an important property because it has a large range of applications. Research in the MOF field has made several advances in terms of multifunctional materials with a focus on magnetic sensor technology [18,113–115]. MOFs are often classified as molecular magnets, in terms of their magnetic properties because of the similarities that exist between traditional molecular magnets and the phenomena that are observed in MOFs. These properties can arise from open-shell organic ligands, which produce magnetic effects by establishing short bridges oxo, cyano, or azido between metals to allow for coupling between the metal centers, or by the use of the intrinsic properties of paramagnetic metals. In order to create magnetic fields that permeate the entire material, it is necessary to design the ligand in such a way that it produces an appropriate topology and allows for efficient interactions between the valence electrons in neighboring example where a ferromagnetic field was produced has been reported by Awaga et al. The compound 1,3,5-trithia-2,4,6-triazapentalenyl TTTACu hexafluoroacetyl acetonato hfac2, creates a ferromagnetic dimer through the interactions of the coordination bond between the Cuhfac2 and TTTA ligands. The zigzag chains created by these bridges are linked into a 2D layer by hydrogen bonding between the S atom on the dithiazolyl ring and the O atoms of Cuhfac2. These hydrogen bonds supply weak inter-dimer antiferromagnetic interactions [116].Antiferromagnetism describes the phenomenon that is observed when a molecule’s spin moment is zero in the absence of an external magnetic field because the adjacent spins alternate in a regular pattern. Gao et al. reported an example of antiferromagnetic interactions in MOFs with his 3D Mn2+ framework. The Mn2+ ions are bridged by μ 3-tetrazolate-5-carboxylate tzc ligands and extended into the final 3D structure by 1,2-bis4-pyridylethane bpea ligands [117].Bu et al. reported a 3D homospin ferrimagnet, in which there exist two antiferromagnetically coupled lattices with uncompensated spin S = 1/2 for every three Cu2+ atoms. Two crystallographically independent Cu2+ centers cause the topological arrangement of the spins to be ordered in such a way that a spin moment is produced at low temperatures [119]. In addition, some frustrated and canting magnetic MOFs as well as the behaviors of spin-crossover and induced magnetic change in MOFs have been reported, but that is beyond the scope of this chapter [120,121].Read full chapterURL P. Aguilar, in Nanomaterials for Medical Applications, Magnetic SensorsMagnetic NPs are used as immobilization platforms in various protein and DNA detection systems for isolation, purification, and eventual detection process using a combination of giant magnetoresistive GMR sensors or magnetic sensors. These offer unique merits of portability, low cost, fast assay, and ease of integration into a disposable lab-on-a-chip. Magnetic sensors are based on physical effects that relate an electrical resistance directly to an external magnetic field, namely the GMR and the tunneling magnetoresistance effect in ultrathin multilayered film These physical effects have been intensively explored within the field of magneto- and spin electronics due to their direct translation of magnetization directions into resistance changes and their scalable size that is compatible with standard complementary metal oxide semiconductor processing. Down to a concentration of about 10 pg/µL of DNA molecules, for example, the magnetoresistive technique is competitive with current standard analysis biosensors utilize a quantum mechanical phenomenon wherein a change in the local magnetic field induces a change in resistance due to spin-dependent scattering in elaborately engineered magnetic multilayer or sandwich films142 which was first demonstrated for biosensors by Baselt in Nontoxic paramagnetic particles ranging from micro- to nanosized particles are linked to various biomolecules enabling highly specific biological cell separations as well as therapeutics144 such as drug-targeting and delivery, cancer therapy, lymph node imaging, and hyperthermia. Aside from iron oxide magnetic NPs, superparamagnetic or ferromagnetic Co and FePt NPs132,145–147 may also be used for separation and therapeutics. The magnetic sensors for detecting biomolecules are fascinating because the nanoparticles can be moved by applying a magnetic field sensitive circuit architecture that is scalable for larger sensor arrays for multiplexing allowing real-time monitoring was reported for clinical They used a custom 1 by cm sensor with sensor-to-sensor pitch of 300 µm containing an eight by eight array of spin-valve sensorants. Each sensor has an area of 90 by 90 µm constructed by combining parallel sets of GMR stripes in series to set the coverage area independently of the resistance with the maximum voltage that can be applied limited to V to avoid breakdown of the thin passivation layer. The sensor used paramagnetic particles ranging from micro- to nanosized particles that were linked to various biomolecules enabling highly specific protein detection. The sensor was used to detect two blinded samples of human CEA spiked into mouse serum. In a 20-min assay, the CEA in the mouse serum samples were established to contain to contain 66 fM CEA for sample A and fM CEA for sample B. The actual mouse serum sample A was revealed to have been spiked with 75 fM CEA while mouse serum sample B contained fM CEA showing a deviation of 12 and 8% respectively. In another study, the researchers also showed the use of MNP tags to detect CEA, lactoferin, and vascular endothelial growth factor with BSA as negative control. The GMR assay with MNP tags were capable of exceptionally sensitive and selective multiplex protein detection in a single reaction well of only 20–50 their study, they used cyano silane surface chemistry on magnetic particles to develop a sandwich assay for the sensitive and specific detection of By using smaller particles, the magnetosandwich assay performance was enhanced with respect to dynamic range and sensitivity but the detection limit was strongly hampered by the high amount of nonspecific background, especially for the smallest 125-nm particles used, which showed the most promising results. This problem was solved by applying a more stringent blocking procedure detecting S100ββ, a diagnostic marker for stroke and minor head injury, in serum samples down to ~ ng/mL over a broad dynamic range ca. two decades. However, the smaller particles might generate smaller magnetic responses because of their lower magnetization, leading to a tradeoff between MNP size for magnetic signal generation and for assay sensors offer rapid, sensitive, and low background methods of detecting important disease biomarkers. With proper choice of MNPs, significant degree of clustering that could lead to irreproducible magnetic sensor results could be avoided with strong blockers. Furthermore, smaller particles allow for improved sensitivity and wider dynamic range of concentration detected. However, smaller particles may generate smaller magnetic responses because of their lower magnetization showing a tradeoff between MNP size for magnetic signal generation and for assay performance. More studies are on-going to launch this system for clinical full chapterURL structure and domain wall dynamics in microwires as determined by the magneto-optical Kerr effectA. Chizhik, in Magnetic Nano- and Microwires, MOKE of submicrometric wiresOne of the interesting branches of our investigation is the MOKE study of submicrometric, glass-covered wires Chizhik et al., 2013. Following the task of miniaturizing the active elements of magnetic sensors, we investigated a series of Fe-rich wires with a metallic nucleus radius, 400 and 700 nm. Performing this study, we demonstrated the possibility of a MOKE technique at the limit of the optical possibility The characteristic size of the wires studied is on the same scale as the eave length of the presents an LMOKE hysteresis loop. It has a rectangular shape that confirms the effect of axial magnetic bistability on a single submicrometric wire. An external tensile stress was applied to the wire to determine the type of magnetic structure. Figure presents the experimental dependence of the coercive field on the square root of the tensile stress . The formation of surface domain wall is the basic process of the surface bistability effect. The surface coercive field is proportional to the energy γ required to form the domain wall involved in the bistable process. Analyzing the MOKE results obtained, we establish the existence of an “inner core–outer shell” magnetic configuration with surface and radial closure domains on the surface of the studied wires. In such a way, we stated that the magnetic bistability effect and the transformation of hysteresis loops induced by stress are observed in extremely thin, submicrometric, Fe-rich, glass-covered Longitudinal magneto-optical Kerr effect dependence on the axial magnetic field in a submicrometric, glass-covered wire with a nominal composition of Dependence of the coercive field on tensile stress in a wire with a nominal composition of full chapterURL and ferrohydrodynamicMohsen Sheikholeslami, Davood Domairry Ganji, in External Magnetic Field Effects on Hydrothermal Treatment of Nanofluid, 2016AbstractMagnetohydrodynamic and ferrohydrodynamic are investigated in this chapter. The existence of a magnetic field has a noticeable effect on heat transfer reduction under natural convection and mixed convection, but in many engineering applications such as magnetic sensors, magnetic storage media, and cooling systems of electronic devices, increasing heat transfer from solid surfaces is a goal. Therefore, the effect of the magnetic field on nanofluid flow and heat transfer has been considered via several examples. There are two models for simulating nanofluid flow and heat transfer single phase and two phase. In the single-phase model, nanoparticles are in thermal equilibrium, and there are not any slip velocities between the nanoparticles and fluid molecules; thus, they have a uniform mixture of nanoparticles. In the two-phase model, the nanoparticles cannot accompany the fluid molecules because of some slip mechanisms such as Brownian motion and thermophoresis, so the volume fraction of the nanofluid may not be uniform anymore, and there would be a variable concentration of nanoparticles in a mixture. Finally, the governing equations for natural convection and mixed convection of nanofluids are presented considering a magnetic full chapterURL

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