Paramagnetic Resonance in the Early Years at the Zavoisky Institute

Abstract

The collaboration of three Kazan physicists: E.K. Zavoisky, S.A. Al'tshuler and B.M. Kozyrev, should be mentioned in the context of the history of the electron paramagnetic resonance discovery. Zavoisky investigated the effect of the high frequency electromagnetic field on substances back in the thirties. At that time he invited physical-chemist B.M. Kozyrev and a bit later theorist S.A. Al'tshuler, who were acquainted with him since his studying in Kazan University, to participate in this work. Their collaboration led to a close friendship that lasted for life.Zavoisky discovered paramagnetic resonance in 1944 in Kazan University (1-3). He worked directly in the field of EPR only for about three years. In 1947 he left Kazan for Moscow and began work at the Kurchatov's Institute. Investigations of paramagnetic resonance in Kazan were continued by Al'tshuler at Kazan University and by Kozyrev at the Kazan Branch of Academy of Sciences. The Physical Technical Institute was founded in 1946 within the Kazan Branch of the Academy of Science of USSR. The Physical department was headed by Zavoisky and, after his departure from Kazan, by Kozyrev. Here we shall mention the main lines of research which were performed in those distant years in Kazan Physical Technical Institute.Studies on transition metal ions were spurred on by a publication from the west (4). A paper from Kazan "On the theory of paramagnetic relaxation in perpendicular fields" (5) published in 1947 was devoted to the analysis of the origin of paramagnetic resonance lines in Mn 2+ , Cr 3+ and Cu 2+ salts measured in the frequency range from 50 MHz to 3.5 GHz. This paper reports a study of the effect of internal local magnetic fields on the magnetic resonance spectrum. The authors concluded that line width and the line shape of the EPR signal depend mainly upon magnetic dipole-dipole interactions of magnetic ions and are affected by exchange interactions between magnetic ions.At the same time the study of the effect of nuclear spin on resonance absorption in solutions of manganese and copper salts was undertaken. In aqueous 0.5 M MnCl 2 , at low frequency of the oscillating field (v = 100 MHz) a single peak of paramagnetic absorption with g = 1 was observed. The weak magnetic field did not break the coupling between the electron and nuclear angular moments, and transitions between Zeeman sublevels of the states with total spin F = I + S were observed. They correspond to g F = g" [F(F+1) + S(S+1) -I(I+1)]/2F(F+1). As I 57 Foundations of Modern EPR Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 10/01/15. For personal use only.