Nobel prize to O. Stern awarded in 1943 "for his contributions to the development of the molecular ray method and his discovery of the magnetic moment of the proton''
Frisch, R.; Stern, O.; Über die magnetische Ablenkung von Wasserstoffmolekülen und das magnetische Moment des Protons. I / Magnetic Deviation of Hydrogen Molecules and the Magnetic Moment of the Proton. I.
Z. Phys. 85 (1933) 4;
Experimental details are given of the method for the determination of the magnetic moment of hydrogen positive rays by magnetic deviation. Measurements with para-hydrogen give a magnetic moment of 1 nuclear magneton; ortho-hydrogen a value of 2 to 3. (Science Abstracts 1933, 5075. W. R. A.).
First measurement of the proton magnetic moment.