A. Gerber, G. Kopnov, M. Karpovsky

Our technique is simultaneous measurement of two parameters: resistivity and magnetization that both affected by the presence of detected gas. Monitoring of two independent parameters is expected to improve selectivity of the gas sensor. Feasibility of the approach is demonstrated by detecting low concentration of hydrogen gas using thin CoPd films as the sensor material. The Hall effect sensitivity of the optimized samples exceeds 200% per 104 ppm of hydrogen, which is two orders higher than the sensitivity of the conductance detection.

• Date: August 2017
• Category: Applied research

Close

Magnetoresistance of granular ferromagnets

A. Gerber, A. Milner, B. Groisman, M. Karpovsky, A. Gladkikh, and A. Sulpice

Granular mixtures of ferromagnet-normal metal (for example Ni-Ag) display a transition from a super-paramagnetic regime to a macroscopic ferromagnetic regime. This transition occurs around the percolation threshold of the ferromagnetic grains. Above the percolation threshold, an anisotropic magnetoresistance is found, while slightly below the percolation threshold, a giant magnetoresistance is observed.

• Date: March 1997
• Category: Fundamental Study

Close

Correlation between the extraordinary Hall effect and resistivity

A. Gerber, A. Milner, A. Finkler, M. Karpovski, L. Goldsmith, J. Tuaillon-Combes, O. Boisron, P. Mélinon, and A. Perez

We propose to reconsider the correlation between the extraordinary Hall effect and resistivity by using the skew scattering model and Matthiesen’s rule to separate contributions of different scattering sources. The model has been experimentally tested for the cases of scattering by magnetic nanoparticles embedded in normal-metal matrix, insulating impurities in magnetic matrix, surface scattering, and temperature-dependent scattering.

• Date: June 2004
• Category: Fundamental Study

Close

Linear Positive Magnetoresistance and Quantum Interference in Ferromagnetic Metals

A. Gerber, I. Kishon, I. Ya. Korenblit, O. Riss, A. Segal, M. Karpovski, and B. Raquet

Positive, linear in field, and isotropic magnetoresistance in fields up to 60 T is found in geometrically constrained ferromagnets, such as thin films of iron, nickel, and cobalt and their granular mixtures with nonmagnetic materials. The resistivity measured as a function of temperature shows a minimum at temperatures reaching a remarkably high 92 K, followed by logarithmic dependence at low temperatures. We propose to explain both phenomena by a modified version of the quantum electron-electron interaction theory. The agreement is only qualitative while the observed magnitude of the magnetoresistance slope is much larger than the calculated one.

• Date: January 2007
• Category: Fundamental Study

Close

Linear Positive Magnetoresistance and Quantum Interference in Ferromagnetic Metals

A. Gerber, A. Milner, G. Deutscher, M. Karpovsky, and A. Gladkikh

We report the results of high magnetic field study of granular 3D Al-Ge and demonstrate that intragranular superconductivity leads in truly insulating samples (with an exponentially diverging normal state resistivity), either to a global superconducting phase coherent state, or to a “superconductor- insulator” state with Cooper pairs totally localized within individual grains, depending on the strength of the intergranular Josephson coupling.

• Date: June 1997
• Category: Fundamental Study

Close

Linear Positive Magnetoresistance and Quantum Interference in Ferromagnetic Metals

A. Gerber, I. Kishon, I. Ya. Korenblit, O. Riss, A. Segal, M. Karpovski, and B. Raquet

Positive, linear in field, and isotropic magnetoresistance in fields up to 60 T is found in geometrically constrained ferromagnets, such as thin films of iron, nickel, and cobalt and their granular mixtures with nonmagnetic materials. The resistivity measured as a function of temperature shows a minimum at temperatures reaching a remarkably high 92 K, followed by logarithmic dependence at low temperatures. We propose to explain both phenomena by a modified version of the quantum electron-electron interaction theory. The agreement is only qualitative while the observed magnitude of the magnetoresistance slope is much larger than the calculated one.

• Date: January 2007
• Category: Fundamental Study

Close

Sixteen-state magnetic memory based on the extraordinary Hall effect

A.Segal, M.Karpovski, A.Gerber

We report on a proof-of-concept study of split-cell magnetic storage in which multi-bit magnetic memory cells are composed of several multilevel ferromagnetic dots with perpendicular magnetic anisotropy. Extraordinary Hall effect is used for reading the data. Feasibility of the approach is supported by realization of four-, eight- and sixteen- state cells.
Highlights
► We propose a novel structure of multi-bit magnetic random access memory.
► Each cell contains several interconnected storage dots.
► Extraordinary Hall effect is used for reading the data.
► Four-, eight- and sixteen-state cells have been realized.

• Date: April 2012
• Category: Applied Study

Close