Observation of higher order NMR larmor lines by SQUID in solids at low magnetic field

• Published in: Journal of low temperature physics Vol. 72; no. 3-4; pp. 319 - 343
• Main Authors: KOHL, M, ODEHNAL, M, PETRICEK, V, TICHY, R, SAFRATA, S
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01-08-1988
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Nuclear magnetic resonance and relaxation; Physics; Magnetization; Magnetic relaxation; Superconducting quantum interferometer device; Theoretical study; Very low temperature; Nuclear magnetic resonance; Experimental study; Magnetic field
• ISSN: 0022-2291; 1573-7357
• DOI: 10.1007/BF00682103

The authors describe an apparatus allowing the observation of the NMR static longitudinal component of nuclear magnetization M sub(z) by a SQUID at low magnetic fields and at T = 4.2 K in Plexiglas, Teflon, and CaF sub(2). The higher order NMR Larmor lines at 2f sub(0), 3f sub(0), and 4f sub(0), where f sub(0) is the Larmor frequency of the allowed NMR line, were measured. These lines correspond to a flip of two, three, and four spins, respectively, by one photon. The amplitudes of 2f sub(0) and 3f sub(0) lines and their field dependences show that the common assertion that the forbidden lines at 2f sub(0) and 2f sub(0) appear in the same order of perturbation theory and that their intensity decreases with static magnetic field B sub(0) as B sub(0)@)u- super(2) is wrong. In fact, the third Larmor line 3f sub(0) appears at higher order than the second Larmor line 2f sub(0) and its intensity decreases as B sub(0)@)u- super(4).