NMR Spin-Echo Spectroscopy in Magnets Using Arbitrary Duration Radio-Frequency Pulses

The work is devoted to the quantum-statistical investigation of echo-processes in magnets excited by a series of radio-frequency arbitrary duration pulses. The obtained theoretical results for the number of echo signals, time moments of their formation and their intensities are in good agreement with experiments carried out on magnets (ferrites, ferrometals, half-metals, manganites). The application of wide RF pulses and their sequences makes it possible to accumulate weak signals, enriches the echo-response spectrum with clearly separated intensive lines, i.e., essentially increases the sensitivity of apparatus and, correspondingly, the possibilities to explore the fine details of dynamical and relaxation processes taking place in nuclear spin-systems with sufficiently long relaxation times. The new experimental results in the study of relaxation processes are given. The high intensity of observed multiple echo signals in lithium ferrite made it possible to establish the nature of fast relaxing component in multiple-echo signal for the first time observed in FeV.