Giant magnetoresistance of semimagnetic semiconductors and applications for magnetic field sensors (original) (raw)
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We present a detailed study of the dielectric and charge transport properties of the antiferromagnetic cubic spinel HgCr2S4. Similar to the findings in ferromagnetic CdCr2S4, the dielectric constant of HgCr2S4 becomes strongly enhanced in the region below 60 - 80 K, which can be ascribed to polar relaxational dynamics triggered by the onset of ferromagnetic correlations. In addition, the observation of polarization hysteresis curves indicates the development of ferroelectric order below about 70 K. Moreover, our investigations in external magnetic fields up to 5 T reveal the simultaneous occurrence of magnetocapacitance and magnetoresistance of truly colossal magnitudes in this material.
Development of Sensors Based on Giant Magnetoresistance Material
Procedia Engineering, 2012
In this review we discuss development of sensors based on giant magnetoresistance (GMR) material.The GMR material has high magnetic and electrical properties, therefore it has great potential as next generation magnetic field sensing devices. During the last decade, intensive research efforts have been expended to develop sensors based on giant magnetoresistance (GMR) material, both based on inorganic materials and organic materials. Many application of GMR sensor, such as: current sensor, linear and rotational position sensor, head recording, and biosensor, are reviewed.
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X-band (-,9.3 GHz) EPR spectra are recorded from room temperature down to 5 K on two samples of symmetry-induced zero band gap semiconductor Hgl_xCo~Se (x=0.0045 and 0.0087), previously subjected to electron bombardment. Both the samples exhibit, in addition to a narrow intense line (g = 2.018) due to trapped electron/ defect centre, a broad Co 2+ EPR line (overlap of the transitions Ms = +1/2 +-* +3/2) characterized by g = 2.027, which disappears at low temperatures. In addition, only the EPR spectra of the sample with the larger concentration of Co ions reveal the presence of an extra EPR line with the value of g = 2.024 at temperatures below 40 K. (This line was, however, found to be present in another sample with the lower concentration.) This extra line is interpreted to be due to the Kramers doublet (Ms = 4-1/2) of the Co 2+ ion. The present EPR data do not indicate the presence of Co 3+ ions.
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Journal of Magnetism and Magnetic Materials, 1997
The low field AC magnetic susceptibility of Hgl_xFe~Se (x = 0.045, 0.070 and 0.095) has been measured in the temperature range 12 150 K. Our experimental data as well as those reported earlier are compared with the extended nearest-neighbour pair approximation calculations taking into account the long-range antiferromagnetic exchange interaction between Fe 2 + ions in the form J(R) = JNN/R'. Good agreement is found between the theory and experiment with 11 K ~< [JNNI ~< 15 K and n = 5.
Chinese Physics, 2003
Amorphous Co x C 1−x granular films were prepared on n-Si(100) substrate by dc magnetron sputtering. The effects of Co concentration, film thickness and annealing temperature on the magnetic properties and magnetoresistance (MR) were investigated. After annealing at 500°C for 0.5 hour, the Co(002) peak of the Co x C 1−x (x>2.5 at.%) films was observed, but cracks appeared in the films. Saturation magnetization M s increased steadily with the increase of Co concentration from 2.5 at.% to 50 at.% and also increased with annealing temperature from room temperature to 400°C. The coercivity of Co x C 1−x films was less than 180 Oe. The as-deposited Co 2.5 C 97.5 granular films with 80 nm thickness showed a highly positive MR, up to 15.5% at a magnetic field of 0.8 T, observed at T=300 K when the external magnetic field was perpendicular to the film surface. With increasing film thickness and annealing temperature, the value of MR was found to decrease gradually and changed from positive to negative. The MR effect of the Co x C 1−x granular films can be explained by p-n heterojunction theory and interface scattering effect.