Detection of hydrogen by the extraordinary Hall effect in CoPd alloys

TL;DR

This study investigates how hydrogen adsorption affects the extraordinary Hall effect in CoPd ferromagnetic films, revealing potential for highly sensitive hydrogen sensors based on magnetic property changes.

Contribution

It demonstrates the hydrogen sensitivity of CoPd alloys via EHE measurements, identifying composition ranges with maximum response and characterizing the effect of hydrogen on magnetic properties.

Findings

Hydrogen adsorption adds a positive term to the EHE coefficient.

Maximum hydrogen sensitivity occurs near 38% Co concentration.

EHE response to low hydrogen concentrations can reach hundreds percent.

Abstract

Effect of hydrogen adsorption on the extraordinary Hall phenomenon (EHE) in ferromagnetic CoPd films is studied as a function of composition, thickness, substrate and hydrogen concentration in atmosphere. Adsorption of hydrogen adds a positive term in the extraordinary Hall effect coefficient and modifies the perpendicular magnetic anisotropy with the respective changes in coercivity and remanence of hysteresis loops. Hydrogen sensitive compositions are within the Co concentration range 20% < x < 50% with the strongest response near the EHE polarity reversal point x_0 ~ 38%. Depending on the film composition and field of operation the EHE response of CoPd to low concentration hydrogen can reach hundreds percent, which makes the method and the material attractive for hydrogen sensing.