Hysteresis, like resistance, is usually lossy. It is a carry-forward effect of the past history of the material.
There are negative versions of each, which imply negentropy - but usually this is framed as negative differential resistance, for instance, which only happens in a narrow part of the curve, so that the net resistance is still positive. With hysteresis effects, either thermal or magnetic, if negative hysteresis is found, it could lead to extreme positive feedback, and be gainful. It was seen in nickel as far back as 1935. http://www.ias.ac.in/jarch/currsci/4/157.pdf Many nickel alloys are superparamagnetic. If superparamagnetic hydrogen/deuterium exchange is found to be gainful, it would be the result of negative hysteresis in the thermo-magnetic properties of the nickel alloy matrix material. Symmetry is lost in the sense that thermal gain on D-loading is not balanced by thermal loss on H-loading as the field oscillates.
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