Well, after an extensive search, I found little in terms of answering your question with reference material. I did find some articles that spoke of hair being a "pollen magnet", which would fall under the classification of static electricity. What you would have to do to synthesize magnetic pollen is use pollen that could have a static charge induced upon it. Static charge is the transfer of electrons from one substance to another. So if you placed the pollen grains inside a container capable of capturing and transferring electrons, that might be a possibility. The excess electrons would be transferred to the pollen, and induce magnetic fields in the pollen grains. The pollen grains would then act as tiny magnets, each having it's own induced magnetic field. They would be attracted to regular magnets and materials that have a net charge of zero, since they have an overall negative charge.