SPIN-FLIP TRANSITION AND FARADAY-EFFECT IN ANTIFERROMAGNET KMNF3 IN MEGAGAUSS MAGNETIC-FIELD

Faraday effect in the antiferromagnet KMnF3 has been investigated in p ulse explosive fields up to 500 T at T = 78 K. The laser wavelength 0. 63 mu m was used in the experiment. The magnetic field dependence of F araday rotation in this antiferromagnet shows a unique feature of a la ck of saturation effect in the fields up to 500 T whereas critical fie ld of spin-flip transition is about 120 T. The theoretical analysis of microscopic nature of Faraday rotation, including the diamagnetic, ma gneto-dipole and paramagnetic mechanisms has been performed. The stron g competition of these mechanisms is important to explain the extremel y small value of the effect and its unusual magnetic field dependence. (C) 1998 Elsevier Science B.V. All rights reserved.