Multiple NMR spin echoes in magnets: The echo structure and potential applications

Abstract

The results of a NMR study of the nature of main multiple nuclear spin-echo components in lithium ferrite are presented. It is shown that the strongly relaxing echo component in lithium ferrite is formed by the stimulated mechanism similar to the one observed in this material earlier for a single-pulse echo.

Two-pulse stimulated echo in magnets

“…Besides it, the observed relaxation dependences could be approximated by the two relaxation processes: the first one being related with the distortion mechanism, and the second one characterized by the much shorter relaxation time most probably could be related with the nonresonant mechanism [2]. Let us note, that the characteristic hump-like shape of SPE signals is observed only at recording echo signals from Similar ones firstly experimentally revealed in work [11] and they could be understood in the frames of the nonresonant mechanism [2,12].…”

“…It was noted unusually short relaxation time of this component as compared with other one ( 1 C component) of multiple echo, which coincides with the signal of usual TPE in the limit of short pulses. The nature of multiple echo components was studied in work [11] on the example of Fe 57 NMR in lithium ferrite where it was simultaneously intensive signals of SPE, TPSE and multiple echoes ( 1 E , 2 E , 1 C and 2 C signals [10]). In work [11] it was revealed the synchronous change of 1 E , 2 E , and 2 C echo signals intensities depending on τ 1 , pointing to the related mechanisms of their formation.…”

“…The nature of multiple echo components was studied in work [11] on the example of Fe 57 NMR in lithium ferrite where it was simultaneously intensive signals of SPE, TPSE and multiple echoes ( 1 E , 2 E , 1 C and 2 C signals [10]). In work [11] it was revealed the synchronous change of 1 E , 2 E , and 2 C echo signals intensities depending on τ 1 , pointing to the related mechanisms of their formation. Besides it, it was established the nature of short relaxation time for 2 C component.…”

“…It was noted unusually short relaxation time of this component as compared with other one ( 1 C component) of multiple echo, which coincides with the signal of usual TPE in the limit of short pulses. The nature of multiple echo components was studied in work [11] C signals [10]). In work [11] it was revealed the synchronous change of T , determined from the Hahn TPE method ( S T 2 =60 μs and 2 T =1200 μs, correspondingly [12]).…”

Multi-quantum echoes in GdAl2 zero-field high-resolution NMR

“…Solomon described the MQ echoes due to the quadrupolar coupling inhomogeneity in solid crystals [15]. Since then, many works have described MQ echo formation in a great variety of materials and interaction strengths and distributions [16][17][18][19][20][21][22][23][24][25]. Echo formation is especially important in the study of magnetic materials, since the great interaction dispersion can let the FID signal vanish before the start of acquisition.…”