Our study concerns nano-objects consisting in an iron oxide core of 10(±2) nm or 20(±5) nm size, which exhibit superparamagnetic behavior, whose shell is constituted of dendrons carrying a dye. The characterization of the magnetic properties of these nano-objects together with their relaxivity into MRI will be presented in this poster. Their detection in an intraoperative context requires an instrument able to detect the extremely weak magnetic signature of the superparamagnetic nanoparticle in a noisy environment. A magnetic probe based on an AC magnetic field excitation of the nano-object coupled to an inductive gradiometer sensor has been designed to achieve this measurement. A conductive layer surrounding the probe is used to provide a shielding, thanks to the eddy current which will limit the leakage magnetic field outside of the probe. The principle of the probe and its ability to measure the magnetic signature of the magnetic nano-objects will be discussed.

Induction sensors are used in a wide range of scientific and industrial applications. One way to improve these is rigorous modelling of the sensor combined with a low voltage and current input noise preamplifier aiming to optimize the whole induction magnetometer. In this paper, we explore another way, which consists in the use of original ferromagnetic core shapes of induction sensors, which bring substantial improvements. These new configurations are the cubic, orthogonal and coiled-core induction sensors. For each of them we give modelling elements and discuss their benefits and drawbacks with respect to a given noise-equivalent magnetic induction goal. Our discussion is supported by experimental results for the cubic and orthogonal configurations, while the coiled-core configuration remains open to experimental validation. The transposition of these induction sensor configurations to other magnetic sensors (fluxgate and giant magneto-impedance) is an exciting prospect of this work.

The present work is focused on high sensitivity (5000 V/T) transverse coiled GMI transducers manufactured with various magnetic materials, magnetically excited at low frequencies (f < 50 kHz) by an insulated coil which is also used for the measurement of the DC and low frequency magnetic field. The impedance and the sensitivity of different types of ferromagnetic material as nanocrystalline ribbons (Finemet) annealed under longitudinal and transverse magnetic fields, as mumetal ribbons and Mn–Zn thin ferrite core are investigated with respect to the static magnetic field. From these results, the differential magnetic permeability is approximated in order to predict sensitivity behavior in relation to the anisotropy magnetic field and the magnitude and the frequency of current excitation.

In this study we address the cross-axis effect (or error) problem in three-axis Anisotropic Magneto Resistance (AMR) magnetic sensors. We focus on magnetometer calibration in the Earth's magnetic field for low-cost sensors. We propose a self-consistent and practical method based on the cross-axis effect modeling, to compensate for the cross-axis effect without using any high precision magnetic sensors for comparing the results. This method does not depend also to other instruments to provide and measure the magnetic field. The compensation method is implemented in two configurations: direct amplification of an AMR signal and magnetization flipping. We show that the residual error with the compensation method in a non-flipped sensor is similar to that sensor in a using flipping.

A 4 nV/√(Hz) at 10 Hz preamplifier with a 12-mW power consumption in complimentary metal-oxide-semiconductor 0.35 μm technology has been developed to go one step further in the integration of the preamplifier of a search coil magnetometer. The present application-specific integrated circuit (ASIC) preamplifier, combined with a 10-cm length, 12-mm diameter, and 15 000 turns search coil sensor demonstrates a noise equivalent magnetic induction as low as 2 pT/√(Hz) at 10 Hz and 14 fT/√(Hz) at 4 kHz. The measured current noise is only 46 fA/√(Hz). AC magnetometers (from 100 mHz to a few kHz) based on search coil sensors are used for space plasma physics investigations because of their excellent robustness and very high sensitivity. The present ASIC preamplifier offers a way to considerably save weight, volume, and power. This paper will focus on the design of the ASIC, driven by the following criteria: low thermal and 1/f noise, radiation hardness for space purpose, and power consumption.