I do not know enough about the process to state the extent of the effect. Or the maths behind it. All I have at this stage is a likely mechanism that would logically effect the rate of decay.
Translation; "I have no idea how radiometric decay works, but I bet that magnetism explain it away. Yeah! Magnets! I believe this because of reasons."
You might as well suggest that the rise in temperature affected the decay rate. You'd have exactly the same amount of evidence for it.
Its more the 0- 600 million ya period that I dispute, I believe it represents a 0-6500 ya period.
Why that date? What's so special about 600 mya?
Mutate and Survive