Probably yes. Why I have written probably? Hydrogen atom is so small and can occupy positions between larger atoms. Such behavior could change the distances between Co-Co atoms and also change exchange interaction. If you know lattice constant of Co and compare it with Co(H) sample, you can calculate distances between atoms. Then you have Bethe-Slater curve. If you know distances, you know what happens.

https://en.wikipedia.org/wiki/Bethe%E2%80%93Slater_curve

If distance increases, the interactions should decrease. And vice versa. You will see that in BS curve.

Good luck

Greetings

P

May you mean Yafet-Kittel effect. I think the existence of H will affect many parameters in Co crystal like anisotropy constant.

Considering double exchange in the way you do it requires a rather well-defined  local orbital system as the O2p orbitals as in case of exchange via oxygen, which is well-known. That is not the case with hydrogen.

Rather, incorporation of hydrogen into Cobalt is detrimental to the magnetic properties. There are rather "old" studies done in Russia, where this was first shown, if I remember correctly. We have seen the same to happen in Co nanoparticles after we we treated them with hydrogen plasma for reductin to the fully metallic state. It took annealing then, to remove the hydrogen and restore "normal" magnetization.

I am not sure whether we actually cite the old work in one of the three papers on Co particles linked below. If I can find the citation elsewhere (have one or two spots to look for it) I'll come back and let you know.

Article How well does total electron yield measure X-ray absorption ...

Article Effective exchange interaction in a quasi-two-dimensional se...

Article From Colloidal Co/CoO Core/Shell Nanoparticles to Arrays of ...

Unfortunately, I have not found the quote I had in mind, neither in the above papers nor in an unpublished report I wrote around that time. So I give a few added links where diverse results have been published, while the reference I was thinking about is not among them, unfortunately.

Hope that (some of) the other links are useful to you.

http://www.sciencedirect.com/science/article/pii/S0925838899005009

http://www.sciencedirect.com/science/article/pii/S0360319998001487

http://www.sciencedirect.com/science/article/pii/S0360319996000663?via%3Dihub

http://www.sciencedirect.com/science/article/pii/S0039602800005264

http://avs.scitation.org/doi/abs/10.1116/1.578405?journalCode=jva

http://www.sciencedirect.com/science/article/pii/S0925838898008457

Article “Magnetic dead layers” on chemisorption at ferromagnetic surfaces

Article Ferromagnetic resonance in the study of surface demagnetizat...