[Balgair]

For Cosmic Rays the only thing is just a lot of atomic nuclei. You need pure mass. This is why a transit to Mars or Saturn is going to be hard for us to pull off in the near term. All those nuclei are expensive to get into orbit right now.

Outside of that, there is a 'graded Z' shield. Here, you make a layer cake of various atomic nuclei (the Zs), going from heavier to lighter. Typically Tantalum down to Tin and down to Aluminum. They physics here aren't super important, but for lower energy radiation, you can get down to a 60% mass reduction for similar shielding protection.

The problem is that it's the higher energy radiation that you are worried about, the Cosmic Rays. Graded Z shields pretty much work like anything else at those energies. Under our current physics mumbo-jumbo, you just need nuclei.

[Miraste]

Artificial magnetic fields are another possible solution.

[Balgair]

Yeah, for the less energetic stuff. The same issue applies, the very energetic stuff just sails right on in. Big EM fields also don't deflect neutrally charged stuff like Cosmic Rays and neutrons. Radiation shielding is hard stuff and it'll take multiple methods working in tandem.