The nuclear spin-echo signals under combined action of magnetic field and RF pulses

Abstract

The effect of a pulse magnetic field on formation of the single-pulse echo signal in some magnetic materials has been studied. The signals of nuclear-spin echo formed by the combined action of radio frequency and magnetic pulses have been observed. The duration of the magnetic pulse was only limited by the length of the radio frequency pulse. The echo signal formed by the two magnetic pulses, the edges of a long magnetic pulse, and other situations that allowed us to reproduce the analogue of multipulse action, were observed as well.This work deals with the action of an applied pulse of magnetic (M) field on the process of single-pulse (SP) echo formation. The SP echo is a resonance response of a spin system to the action of a single radio frequency (RF) exciting pulse. This response arises after the termination of the RF pulse at the time a, which is approximately equal to its duration. A large number of works (see the recent review [1]) was devoted to the investigation of the nature of the SP echo. Nevertheless, this question has not been finally clarified so far.The SP echo formation mechanisms can be conditionally subdivided in groups as follows: the so-called edge-type mechanisms similar to nonresonance mechanism [2] and the mechanism of pulse distortion [3], when the fronts of the RF pulse act as two resonance RF pulses [4] and the mechanisms of intrinsic n'ature of SP echo formation [1,5].The role of the edges of RF pulses was investigated in [6] within the framework of SP echo method in magnets. The investigation was carried out using a low-frequency magnetic field. Hexagonal cobalt and lithium ferrites were chosen as the objects of the investigation. These specimens are interesting due to approximately equal intensities of two-pulse (TP) echo signals in both, whereas the intensity of the SP echo in lithium ferrite is much weaker. The effect of echodecay envelope modulation which is the characteristic for TP echo in cobalt,

On some new modulation effects in magnetic resonance

“…The experimental setup consisted of the resonance probe of a nuclear magnetic resonance (NMR) spectrometer [12] combined with the acoustic resonator (Fig. 3).…”