This paper reports on a magnetic device with a [Co 40 Pd 60 /Cu] 10 /Fe structure for use in the detection of H 2 . In a magneto-optical, transport, and gas-detection system, the proposed device presented sharp, reproducible H 2 -dependent magnetic/electrical properties. The device's saturation magnetization (induced resistance change) dropped (increased) by a factor of ∼5 when a H 2 pressure of 75 kPa is given. Besides, the electrical signal-to-noise ratio of the device can be restored ∼50% by exposing it to a magnetic field of 1000 Oe, even when the sensitivity of the device dropped at a low H 2 pressure (0.7 KPa). This demonstrates the applicability of the device for use as a low-pressure H 2 detector. Operando x-ray spectroscopy revealed that changes in H 2 -induced magnetism arose from a Co-Pd charge transfer effect coupled to changes in the local-structure symmetry.