Investigation of multiple echo signals formation mechanism in magnet at excitation by two arbitrary radio-frequency pulses

TL;DR

This paper presents a quantum-mechanical analysis of multiple spin echo signals generated by two arbitrary RF pulses in a magnet, predicting up to thirteen signals and confirming findings with experiments on lithium ferrite.

Contribution

It introduces a detailed quantum-mechanical model for multiple echo formation with arbitrary RF pulses and predicts the maximum number of signals, validated by experiments on lithium ferrite.

Findings

Up to thirteen echo signals can be formed under fixed RF pulse parameters.

Four primary stimulated echo signals are predicted to appear.

Experimental results on lithium ferrite confirm the theoretical predictions.

Abstract

The quantum-mechanical calculations of intensities and time moments of appearance of multiple spin echo signals of excitation of nuclear spin system of magnet by two arbitrary width radio-frequency pulses were carried out. This method was used by us earlier at consideration of multiple-pulse analogs of single-pulse echo in multidomain magnets upon sudden jumps of the effecting magnetic field in the rotating coordinate system during the action of radio-frequency pulse. The formation mechanisms of echo signals are discussed. The appearance of four primary stimulated echo signals is predicted. The total number of echo signals at fixed parameters of radio-frequency pulses does not exceed thirteen ones. Theoretical conclusions are in compliance with experiments carried out on lithium ferrite. As it was established by us earlier in this magnetic dielectric, in difference from ferrometals, it is observed very short relaxation times of single-pulse and two-pulse stimulated echoes, and the contribution of radio-frequency pulse fronts distribution mechanism is insignificant. For this reason lithium ferrite is a good material for the experimental verification of theoretical conclusions in experimental conditions most close to the theoretical model.