Could a cavity magnetron be used for infrared instead

[lufc888]

of microwaves?

 

[rootone]

Microwave magnetrons are useful because they produce an EM frequency which water molecules are highly effective at absorbing.
I can't think of a reason why similar technology couldn't be used to generate infra red frequencies, but there are many ways to generate IR that are probably more efficient.
A standard electric bar fire element probably is.