An original model to predict microfluxgates output voltage is presented. First, the limits of the classical analytical demagnetizing factor model are exhibited thanks to a comparison with measurements. Then, an anhysteretic non-linear numerical integral model, based on the Method of Moments, is proposed to compute magnetization correctly at each point of the cores and at any moment. Output voltage is finally deduced from magnetization variation. Sensitivity measurements of the second harmonic on a microfluxgate have confirmed this approach.

Low cost and low power consumption are key factors to the spreading of microsystems into the everyday life tools. Fluxgate magnetometer systems still request such an improvement. This paper presents compact thin film microfluxgate sensors working in the range of tenths of kHz to tenths of MHz which exhibit improved factor of merit (FOM) in the high frequency range when the sensor size is reduced. The architecture is based on interlaced excitation and detection solenoid coils wounded around two rectangular cores made of thin film soft magnetic sputtered NiFe permalloy material. Measurement axis and magnetic hard axis are along core length. These thin film sensors also proved to be working in a wide range of excitation currents since deep saturation is not requested thanks to a highly nonlinear hysteresis loop. Excitation currents as low as 6mA lead to still linear output response. Devices with monolayer cores were measured up to 20MHz. Laminated cores were measured up to 73MHz. Frequency response higher than 100MHz is achieved when magnetostatic coupling occurs between laminated layers. The power consumption can be monitored at system level to adjust the sensor sensitivity within a range of 0.5 to more than 220V/T.

5.6 mm times 5.6 mm integrated toroidal inductors with reduced thickness down to 200 mum have been realized. A high inductance-to-dc resistance ratio have been achieved using a toroidal geometry. The realization features thick Cu winding and a thick laminated Ni80 Fe20 core with crossed anisotropy. Impedance measurements have been performed up to 100 MHz with dc bias current applied. As a typical result, we show an inductor with an inductance of 500 nH up to 10 MHz and a dc resistance of 95 mOmega. To the best of our knowledge, this is the highest inductance-to-dc-resistance ratio demonstrated by a fully integrated inductor. This demonstrates the interest of such integrated inductors to replace discrete components in compact low-power modules

5.6×5.6×0.5mm 3 integrated toroidal inductors with high L/R DC ratio have been fabricated on Si substrates with microelectronics tools. The realization features thick layer Cu and Ni 80 Fe 20 technologies. Impedance measurements have been performed up to 100MHz. As a typical result, we show an inductor with L~500nH up to 10MHz, R DC ~110mΩ. To our knowledge, it is the best compromise shown so far. This demonstrates the interest of such integrated inductors to replace discrete ferrite inductors for compact power modules for mobile communication circuits.

Two different technological types of microfluxgate sensors that able to cancel magnetic instabilities and measure magnetic field at the nanoTesla level are presented. The first type has a flat conductive layer deposited inside, above or under the technological solenoidal stack while the second one has a conductive solenoidal coil (with a magnetic core) deposited at the same levels as the microfluxgate technological stack. The effect of stabilization of the output signal of these microfluxgates is investigated.

Two-port coplanar ferromagnetic inductors using solid magnetic planes were fabricated on silicon. L, R, and Q measurements are presented. Cutoff frequencies exceed 10 GHz, indicating no capacitance limitation. The increase in L over the air-core value is /spl sim/15%, and the quality factor Q is of /spl sim/10 up to 1.5 GHz. The inductance scales with HA-alignment and spiral excitation ratio. Agreement with High-Frequency Structure Simulator simulations including ferromagnetic resonance led to a better understanding in terms of L and Q. Current increase in L is limited by the film thickness (0.2 /spl mu/m). Thicker films (0.5-1 /spl mu/m) would lead to larger gain over L (23% to 31%) with similar Q (/spl sim/10). The restriction in Q from the air-core inductor consists in magnetic losses but not only. Another contribution would come from anomalous ohmic losses from the spiral itself enhanced by the proximity of the magnetic planes.

Microfluxgate sensors are intended for the measurement of the very small variations of the earth magnetic field. Our sensors would present an output signal with a basic noise of about 1 nanotesla (nT)/rootHz, if an additional noise in the form of instabilities didn't regularly occur, increasing the output noise by regular jumps of 100 nT in the output signal. Some solutions are presented here to reduce and finally to suppress this problematic noise.

This paper investigates the high frequency (HF) characterization of spiral inductors on various Si substrates. Some of them were chemically anodized in order to form a thick porous Si layer, which provides a low substrate loss and greatly enhanced inductor quality factor. The HF performance and behavior of these inductors have been analyzed by modeling and parameter extraction in order to compare all the substrates.

Soft ferromagnetic zero-magnetostrictive Co Nb Zr thin films have been dynamically deposited by dc planar magnetron sputtering onto continuously transported substrates. No magnetic field has been applied to the films during deposition. The films reveal a well-defined in plane uniaxial anisotropy with an easy axis aligned along the direction of substrate motion. As a result, an anisotropy field of 75 Oe and a ferromagnetic resonance frequency of 2.6 GHz have been measured. The study of the relationship between magnetic properties and film thickness points out a critical thickness around 0.3 μm, above which the films exhibit a stripe-domain-like behavior which is detrimental for the high frequency use. The thermal stability of the films is found to be usual as regular amorphous core materials (stable up to 300°C). Additionally, it is shown that the films do not suffer from rotatable magnetic anisotropy usually observed inconventional statically deposited films under magneticfield. Finally, a different origin of the magnetic anisotropyis suggested in dynamically deposited films.

Noise in NiFe/Ag giant magnetoresistive (GMR) multilayers and in magnetic field sensors based on this material has been studied in order to evaluate the potential of such material and such sensors for low field applications. GMR stripes were used to study the material intrinsic noise for varying DC sense current density, applied field and device dimensions. Noise measurements were then carried out on a magnetic field sensor for which thermal and magnetic characteristics have also been studied. The noise in NiFe/Ag multilayers is dominated by a 1/f noise at low frequencies and shows a flat spectrum at higher frequencies due to Johnson noise. The 1/f noise increases with the current density and is field and device-dimensions dependent. Magnetic field sensors based on NiFe/Ag are good candidates for the realization of low field micromagnetometers because they have suitable characteristics and relatively low noise.

This work describes the fabrication of a giant magnetoresistive field sensor based on NiFe/Ag multilayers. The stacking of the 21 bilayers of NiFe and Ag deposited at liquid nitrogen temperature on a (100) Si substrate has a surface roughness as low as 0.3 nm, which contributes to the good magnetoresistive properties of the material. Owing to a magnetoresistance ratio ΔR/R of 12% under a saturation field of 160 Oe (12.7 kA/m) and a good thermal stability after an annealing at 180°C, this material has been integrated into sensors through microelectronics processing. The particular design of the Wheatstone bridge which constitutes the sensor allows to bias the four active magnetoresistors with only two small magnets stuck along the bridge arms. Such a sensor presents a linearity better than ±2% over a field range of ±35 Oe (±2.8 kA/m) for temperatures ranging from room temperature to 100°C. Hysteresis was evaluated to be smaller than 1 Oe. As a consequence of these good performances without any signal conditioning, this sensor may be considered for applications requiring low fabrication costs such as automotive ones.

Micromagnetometre a porte de flux a saturation magnetique homogene.Selon l'invention, les proprietes geometriques ou magnetiques du coeur sont telles que, lorsque la saturation est etablie dans la zone d'excitation, elle l'est aussi hors de cette zone. On peut, par exemple, elargir les zones d'excitation (Ze), ou ajouter des surepaisseurs, ou utiliser des materiaux a plus forte aimantation a saturation dans la zone d'excitation.Application en magnetometrie.

Planar Silicon Heads (PSH) have been developed in order to offer to the drive industry a modern approach to make heads which are the key component for magnetic recording. Full batch processes manufacturing like integrated circuits, higher performances and largely open for future drive industry are the three main drivers of these new heads. After a long period of development, industrialization and qualification, these heads are now commercially available.The optimization of PSH improves the write capability with a small gap length. The development of a flux concentrator and its optimization comparing modelling and experimental results enabled us to make a very efficient head.This paper describes the flux concentrator acid its optimization.

Because of its optical index, hydrogenated amorphous silicon a-Si:H can be used to make very thin (200–400 Å) slab waveguides on low index substrates. Propagation characteristics of such layers deposited on fused silica substrates are studied in the wavelength range 0.7 to 1.4 μm. It is found that attentuation is mostly due to scattering losses except close to the short wavelength limit where a-Si:H intrinsic losses are becoming important. Useful and probably still improvable propagation characteristics are obtained in the range 1.2–1.4 μm which presently bears a great practical importance. Main interest of these results lies in (i) possibility of fabricating optical integrated devices in which the substrate could be the active material; (ii) possibility of using this type of guide as a "surface enhancement" structure.

The purpose of this work is to realize by R.F. sputtering two stacked photovoltaic structures in view of increasing the conversion efficiency of hydrogenated amorphous silicon solar cells. The dual Schottky structure must enhance the short-circuit current Jcc by an electrical parallel connection of two diodes, while the twin (dual) p-i-n structure must double the open circuit voltage Voc by in-series connecting two junctions. We have first elaborated elementary Schottky and p-i-n diodes which have been electrically investigated. P-i-n diodes offer better Voc but weaker Jcc than Schottky diodes. Good tunnel junctions have been realized and have allowed to double the value of Voc in stacked p-i-n structures. On the other hand, the attempt to make dual Schottky structures was not successful, resulting in low Voc values without any increase of Jcc. These results prove that an effective enhancement of the efficiency will be possible only with multispectral stacked junctions.