Coherent Raman scattering from magnetic excitations in diluted magnetic semiconductors: Bulk crystals of Cd1-xMnxTe

Coherent Raman scattering is applied in the investigation of electronic tra nsitions in diluted magnetic semiconductor Cd1-xMnxTe bulk crystals (0.05 l ess than or equal to x less than or equal to 0.70) in the temperature range between 1.7 and 100 K and in magnetic fields B up to 7 T. Free carriers, p hotoexcited by the high power radiation used, have enabled the observation of the conduction-band free-electron spin hip in alloys nominally free from donors. Apart from the absence of the bound magnetic polaron feature, this free-electron spin-flip transition shows characteristics revealed by the s pontaneous Raman scattering from donor bound electrons. Besides the foe-ele ctron spin flip, in the regime of large manganese contents (x greater than or equal to 0.2) and low temperatures we observe the Raman antiferromagneti c resonance showing a finite Raman shift at B=0, a dependence of the Raman shift linear with magnetic field, corresponding to an effective g factor la rger than 2, and a large linewidth up to 3.5 cm(-1). For small Mn contents (x less than or equal to 0.2) and high temperatures, the paramagnetic reson ance of electrons within the Zeeman multiplet of the S= 5/2 ground state of Mn2+ is observed. The effective g factor is equal to 2 in this case and th e linewidth markedly narrow, e.g., 0.2 cm(-1) for x = 0.10. The temperature dependence of the observed Raman shifts connected with magnetic ordering p oints to a paramagnetic to spin glass phase-transition temperature somewhat below 20 K for x = 0.40 (B = 6 T). In contrast, the corresponding linewidt hs decrease continuously with increasing temperature but remain larger than for x = 0.10 even at T = 80 K; the latter sample is paramagnetic in the wh ole temperature range. [S0163-1829(98)06248-1].