Magnetic resonance in MnSe near the phase transition point

Abstract

W e i s an antiferromagnetic semiconductor with cubic NaCl structure. The present paper discusses investigations on magnetic resonance in MnSe polycrystalline powders in the range from 140 to 300 K. 0 Crystals of MnSe were obtained by vapour transport reaction (1). Stoichiometric and selenium 5 N were destillated under a pressure of 10 tion of iodine was 3 mg/cm and the temperature of source and growth regions wert 915 and 870 C, respectively. The habit of crystals were octahedra of edge length 1 mm. amounts of manganese and selenium were used. Spectrally pure manganese -5 Torr. The concen,,..3 0 The measurements were performed with an X-band (9.3 GHz) microwave spectrometer. The temperature was stabilized automatically and measured with acopper-constantanthermocouple with accuracy of 1 deg. A broad EPR line with g = 1.930 was observed in the paramagnetic region. The line was broadened asthe temperature was reduced in the direction of the NBel temperature (Fig. 1).The shape of the EPR line was tested by the 1: method, It depends on temperature until about 150 K it has Lorentzian shape and below this temperature it becomes asymmetric. The linewidth measurements were fitted by a relation predicted theoretically by Huber (2) 2 0 T -TN -r A € I = A ( 7 ) + B , 0where A = 200 G, paper a r e the peak-to-peak magnetic field separation in the absorption derivative.The magnetic strength and the linewidth were measured by means of an NMR m a gnetometer.r= 0 . 6 0 , B = 0 , T = 132 K. The linewidths reported in this N Experimental results cannot by described by any of the existing theories (2 to 1. These results a r e in good accordance with Battles' (5) 4) which predict