What is diamagnetic in diamagnetic dilution? I'm reading a paper where the authors study a peptide solution where each peptide may have two spin labels attached to them. They put the peptides on the surface and study them using a diamond sensor.

They perform the experiment in two ways. First, they put only peptides with attached spin labels. Then, they dilute the solution with peptides that do not have spin labels, in a ratio 1:10.

They refer to this dilution as "diamagnetic dilution". I do not know why it's called diamagnetic. I've tried to look for a definition but the term only appears in highly technical papers that I can't understand very well.

Does anyone know why this is called "diamagnetic dilution"?

Ben

Edit: The article I'm referring to is this one:

https://advances.sciencemag.org/content/3/8/e1701116

But my question is general.
The term diamagnetic dilution (in general) implies that the material used for dilution has all its electrons paired, so we will not see its response in an electron spin resonance experiment or any other experiment which can sense unpaired spins.