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This paper investigates the use of field gradients, generated by dc currents flowing through gold microcurrent lines in synchronization with external dc fields, to control the position of superparamagnetic beads on the surface of micro-Hall biosensors. The current lines were designed to enable large movements of magnetic beads under small currents thus limiting sample heating that may adversely affect...
New bio-detection methods based on giant magnetoresistance (GMR) or tunneling magnetoresis-tance (TMR) sensors and magnetic nanoparticles are attracting much attention due to their high sensitivity and low cost. In literature, signal to noise ratio (SNR) is often used to estimate detection limit. However, because the actual bio-signal is obtained by differentiating signals before and after biological...
All-metallic giant magnetoresistive (GMR) sensors in a current-perpendicular-to-plane (CPP) geometry are attractive candidates for future high-density recording sensors due to their low intrinsic resistance. With increasing recording density the cross-sectional area of CPP sensors (such as TMR or GMR sensors) must also decrease, resulting in a rapid increase in sensor impedance unless the RA product...
Room-temperature (RT) sample scanning superconducting quantum interference device (SQUID) microscopy (SSM) is a very powerful and promising technique for imaging magnetic field distributions . A SQUID microscope with interchangeable sensor configurations for imaging magnetic fields of room-temperature (RT) samples with sub-millimeter resolution was developed. The sensors are mounted in the vacuum...
In this paper we study the coupling mechanism between the conduction electrons and the allowed spin wave modes of a micron size system. To achieve this goal we investigate the variation of the giant magneto resistance (GMR) effect in a single spin valve sensor as a function of the spin wave mode excited in the system. We couple ferromagnetic resonance technique on a single sensor with transport measurements...
In this study, in order to investigate the spatial resolution of a giant magneto-impedance (GMI) probe, the probe scanned a microstrip line as a magnetic field source in width direction for various frequencies. Measured spatial property was compared with numerical data by the finite-difference time-domain (FDTD) method.
Extraordinary magneto-resistance (EMR) devices have been fabricated and characterized at various magnetic fields, operating temperatures and current excitations. These devices are comprised of non-magnetic high mobility semiconductors and low resistance metallic contacts and shunts. The EMR devices were fabricated using two e-beam lithography processing. The completed EMR devices were tested between...
This work demonstrate sensors that accomplish this same end by modulating the bias on soft-adjacent-layer (SAL) biased AMR devices and sensing the second harmonic signal. The 2f technique allows us to move the signal above the 1/f noise regime and into a less noisy bandwidth. Noise response of these sensors and demonstrated the scalability of the noise with the volume of the sensor has been measured...
A novel hybrid force sensor system has been produced and successfully shown to be able to measure dynamic kN-level forces. It uses an innovative frequency modulation (FM) based system using an amorphous wire sensor wound around a magnetically biased Terfenol-D rod to detect dynamic, stress-induced changes in magnetisation. The hybrid sensor is able to successfully detect low-frequency sinusoidal forces...
In ubiquitous computing, localization of an radio frequency identification (RFID) tag attracts great attention, since it is a key to interfaces with location awareness such as haptic interfaces and navigations for blind people/mobile robots. Since an RFID tag with carrier frequencies of 135kHz or 13.56MHz has a loop antenna, the tag's position estimation is reduced to localization of a magnetic dipole...
Here we present a design for a magnetic avalanche digital detector (MADD) based on a ferromagnetic ring geometry. The sensor has several advantages over previous designs [Megens, M., et al., 2005]. Firstly it operates in an entirely digital manner, rather than relying on reversible deformations within a ferromagnetic element as has been proposed for use in other single bead sensors [Miller, M., et...
This paper presents a motion control sensor based on magneto-impedance (MI) effect. The device has 6-axis, namely 3-axis accelerometer, 3-axis magnetometer and a signal conditioning IC, in a compact package. Using this 6D (6 dimensional) motion control sensor, the attitude of an object such as a cell phone can be detected. This sensor has been embedded in Vodafone 3G mobile phone.
This paper investigates the working modes of orthogonal fluxgate sensor in pulse current excitation approach. A sensitivity of 6.7 mV/muT was obtained at a pulse frequency of 1 kHz with current amplitude of 20 mA and duty cycle of 0.04%. The power consumption of the sensor head could be as low as 6.4 muW, which shows great potential in application for sensors array and portable sensor devices. The...
This paper reports a new micromachined fluxgate sensor with extremely low power consumption using a localized core saturation method. The extremely low power consumption has been achieved by shrinking the magnetic core width wound by the sensing coils, 10 times smaller than that wound by the excitation coils. With such core configuration, the magnetic field within sensing coils will be enhanced several...
This paper investigated the effects of flux concentrators (FCs) on magnetic 1/f noise in magnetoresistive sensing devices. This is done by comparing results for the cases of bare (without FCs) sensors and those with FCs. It is shown that FCs can be a source of broad-band low frequency noise in AC MEMS flux concentrator device when the signal modulation amplitudes are sufficiently high.
A high-frequency MFM (HF-MFM) is built up for the observation of the high-frequency stray fields of harddisk write heads, using a commercial AFM/MFM system as a basis. In this contribution, the amplitude-modulation technique were employed, where an amplitude-modulated current was applied to the head coil in order to detect the force gradient induced by the HF magnetic field. The piezo element is still...
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