Hall effect spintronics for gas detection

Abstract

We present the concept of magnetic gas detection by the Extraordinary Hall effect (EHE). The technique is compatible with the existing conductometric gas detection technologies and allows simultaneous measurement of two independent parameters: resistivity and magnetization affected by the target gas. Feasibility of the approach is demonstrated by detecting low concentration hydrogen using thin CoPd films as the sensor material. The Hall effect sensitivity of the optimized samples exceeds 240% per 104 ppm at hydrogen concentrations below 0.5% in the hydrogen/nitrogen atmosphere, which is more than two orders of magnitude higher than the sensitivity of the conductance detection

Visualizing hydrogen diffusion in magnetic film through magneto-optical Kerr effect

“…This was because Pd is a highly efficient catalyst for hydrogen molecule dissociation and Pd-hydride formation is energy favorable 2 . Based on these findings, we also observed appreciable magnetic modulation in Pd-rich magnetic alloy thin films, indicating that such materials would be useful in fabricating gas sensors and especially suitable for spatially resolved hydrogen diffusion 12,[18][19][20][21][22][23] . Moreover magneto-optical Kerr effect (MOKE), originating from the optical property and magnetism of materials, has long been widely applied in magnetic measurement of nanoscale samples because of the extremely high sensitivity and feasibility [24][25][26] .…”

Reversible 90-Degree Rotation of Fe Magnetic Moment Using Hydrogen

“…Furthermore, hydrogen absorption and desorption can induce reversible changes in magnetic coercivity, remanence/saturation ratio, magnetic moment, magnetic anisotropy energy, and microscopic domain wall motion 15 – 18 . These observations demonstrate the potential for using spintronic devices as hydrogen gas sensors 6 , 19 – 21 . Magnetic interlayer exchange coupling, also known as Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling, has been widely studied through the application of giant magnetoresistance (GMR) in magnetic storage and magnetic field sensors 22 , 23 .…”

Enhancement of Anomalous Hall Effect via Interfacial Scattering in Metal‐Organic Semiconductor Fex(C60)1−x Granular Films Near the Metal‐Insulator Transition

“…The R xy values of conventional ferromagnetic metals are much lower than those of semiconductors such as Si and Ge, so ferromagnetic metals cannot replace semiconductors in Hall sensors. In 1995, Pakhomov et al found that the granular film can increase AHE by several orders of magnitude compared with ferromagnetic metals, making the application of AHE promising . Thereafter, similar enhancements were observed in various magnetic metal‐insulator granular films …”

“…Different scaling laws between anomalous Hall resistivity (ρ AH ) and longitudinal resistivity (ρ xx ) have been exploited to describe these physical origins: both intrinsic spin‐orbit coupling and extrinsic side jump mechanism obey , while extrinsic skew scattering mechanism satisfies ρ AH ∝ ρ xx . These scaling laws have been valid in many systems, including magnetic metals, alloys, single crystalline or polycrystalline compounds, etc., but usually invalid in inhomogenous ferromagnetic systems, such as granular films around the percolation threshold with resistivity between typical metal and insulator . Some researchers reported that the interface scattering plays a significant role and influences the AHE evidently in these granular systems .…”