Hideki Yukawa
In 1934, Tamm and Semen Altshuller suggested that the neutron has a non-zero magnetic moment, the idea was met with scepticism at that time, as the neutron was supposed to be an elementary particle with zero charge, and thus could not have a magnetic moment. The same year, Tamm coined an idea that proton-neutron interactions can be described as an exchange force transmitted by a yet unknown massive particle, this idea was later developed by Hideki Yukawa into a theory of meson forces.