Gyromagnetic Effects

Gyromagnetic Effects 

a group of effects arising from the interrelationship between the magnetic and mechanical moments of microscopic particles, which are carriers of magnetism. Any particle with a definite angular momentum (an electron, proton, neutron, atomic nucleus, or atom) also has a definite magnetic moment. As a result, an increase in the angular momentum of a system of microscopic particles (that is, a physical body or specimen) generates an additional magnetic moment in the specimen, and conversely, the specimen acquires additional mechanical moment upon magnetization.

Table 1. Main characteristics of the most important hard-magnetic materials
	Basic composition (percent by weight)	Br x 1Q-3 (gauss)	Hc (oersteds)	(8H)max (megagauss · oersted)
U13 ........	1 .3 C; remainder Fe	8	60	0.22
E7V6 ........	0.7 C, 0.4 Cr, 5.7 W, 0.4 Si; remainder Fe	10.4	68	0.36
EKh9K15M ........	1 C, 9 Cr, 15 Co, 1.5 Mo; remainder Fe	8.2	160	0.55
12KMV12 (Comol) ........	12 Co, 6 Mo, 12 W; remainder Fe	10.5	250	1.1
luND4 (Alni) ........	25 Ni, 12 Al, 4 Cu; remainder Fe	6.1	500	0.9
luNDK24 (Magnico) ........	14 Ni, 8 Al, 24 Co, 3 Cu; remainder Fe	12.3	600	4
luNDK35T5VA (Ticonal) ........	14 Ni, 8 Al, 35 Co, 3 Cu, 5 Ti, Nb < 1	10	1,500	10
PIK76 (Platinax) ........	76 Pt; remainder Co	7.9	4,000	12
52KF13 (Vicalloy) ........	52 Co, 13 V; remainder Fe	6	500	—
2FK (Co ferrite) ........	COO-Fe203	3	1,800	2
1 Bl (Ba ferrite) ........	BaO-6Fe2O3 (isotropic)	2	1,700	1
3BA (Ba ferrite) ........	BaO-GFeaOa (anisotropic)	3.7	2,000	3.2
3SA (Sr ferrite) ........	SrO-6Fe203 (anisotropic)	3.6	3,200	3
SmCo5 ........	SmCos (anisotropic)	9.4	8,500	21

The generation of a magnetic moment (magnetization) in ferromagnetic samples upon rotation was first discovered in 1909 by S. Barnett. The opposite effect—the rotation of a freely suspended ferromagnetic specimen during its magnetization in an external magnetic field—was discovered in 1915 in the experiments of A. Einstein and W. de Haas.

Gyromagnetic effects make possible the determination of the ratio of the magnetic moment of an atom to its total angular momentum (the gyromagnetic ratio) and the drawing of conclusions regarding the nature of carriers of magnetism in various materials. Thus, the magnetic moment in the three d-metals (iron, cobalt, and nickel) was found to result from the spin moments of the electrons. A magnetic moment may be generated in other materials (such as the rare earths) by both the spin and orbital moments of the electrons.

In connection with the creation of new methods, mainly resonance methods, for the study of magnetism, interest in gyromagnetic effects has decreased considerably.

REFERENCES

Dorfman, Ia. G. Magnitnye svoistva istroenie veshchestva. Moscow, 1955.
Vonsovskii, S. V. Magnetizm. Moscow, 1971.
Scott, G. “Review of Gyromagnetic Ratio Experiments.” Reviews of Modern Physics, 1962, vol. 34, no. 1, p. 102.

R. Z. LEVITIN